array to array assignment in c

Learn C practically and Get Certified .

Popular Tutorials

Popular examples, reference materials, learn c interactively, c introduction.

• Getting Started with C
• Your First C Program

C Fundamentals

• C Variables, Constants and Literals
• C Data Types
• C Input Output (I/O)
• C Programming Operators

C Flow Control

• C if...else Statement
• C while and do...while Loop
• C break and continue
• C switch Statement
• C goto Statement
• C Functions
• C User-defined functions
• Types of User-defined Functions in C Programming
• C Recursion
• C Storage Class

C Programming Arrays

C Multidimensional Arrays

Pass arrays to a function in C

C Programming Pointers

Relationship Between Arrays and Pointers

• C Pass Addresses and Pointers
• C Dynamic Memory Allocation
• C Array and Pointer Examples
• C Programming Strings
• String Manipulations In C Programming Using Library Functions
• String Examples in C Programming

C Structure and Union

• C structs and Pointers
• C Structure and Function

C Programming Files

• C File Handling

C Files Examples

C Additional Topics

• C Keywords and Identifiers
• C Precedence And Associativity Of Operators
• C Bitwise Operators
• C Preprocessor and Macros
• C Standard Library Functions

C Tutorials

• Find Largest Element in an Array
• Calculate Average Using Arrays
• Access Array Elements Using Pointer
• Add Two Matrices Using Multi-dimensional Arrays

An array is a variable that can store multiple values. For example, if you want to store 100 integers, you can create an array for it.

How to declare an array?

For example,

Here, we declared an array, mark , of floating-point type. And its size is 5. Meaning, it can hold 5 floating-point values.

It's important to note that the size and type of an array cannot be changed once it is declared.

Access Array Elements

You can access elements of an array by indices.

Suppose you declared an array mark as above. The first element is mark[0] , the second element is mark[1] and so on.

Few keynotes :

• Arrays have 0 as the first index, not 1. In this example, mark[0] is the first element.
• If the size of an array is n , to access the last element, the n-1 index is used. In this example, mark[4]
• Suppose the starting address of mark[0] is 2120d . Then, the address of the mark[1] will be 2124d . Similarly, the address of mark[2] will be 2128d and so on. This is because the size of a float is 4 bytes.

How to initialize an array?

It is possible to initialize an array during declaration. For example,

You can also initialize an array like this.

Here, we haven't specified the size. However, the compiler knows its size is 5 as we are initializing it with 5 elements.

Change Value of Array elements

Input and output array elements.

Here's how you can take input from the user and store it in an array element.

Here's how you can print an individual element of an array.

Example 1: Array Input/Output

Here, we have used a  for loop to take 5 inputs from the user and store them in an array. Then, using another  for loop, these elements are displayed on the screen.

Example 2: Calculate Average

Here, we have computed the average of n numbers entered by the user.

Access elements out of its bound!

Suppose you declared an array of 10 elements. Let's say,

You can access the array elements from testArray[0] to testArray[9] .

Now let's say if you try to access testArray[12] . The element is not available. This may cause unexpected output (undefined behavior). Sometimes you might get an error and some other time your program may run correctly.

Hence, you should never access elements of an array outside of its bound.

Multidimensional arrays

In this tutorial, you learned about arrays. These arrays are called one-dimensional arrays.

In the next tutorial, you will learn about multidimensional arrays (array of an array) .

Table of Contents

• C Arrays (Introduction)
• Declaring an Array
• Access array elements
• Initializing an array
• Change Value of Array Elements
• Array Input/Output
• Example: Calculate Average
• Array Elements Out of its Bound

Video: C Arrays

Sorry about that.

Related Tutorials

Arrays in C – Declare, initialize and access

Array is a data structure that hold finite sequential collection of homogeneous data .

To make it simple let’s break the words.

• Array is a collection – Array is a container that can hold a collection of data.
• Array is finite – The collection of data in array is always finite, which is determined prior to its use.
• Array is sequential – Array stores collection of data sequentially in memory.
• Array contains homogeneous data – The collection of data in array must share a same data type .

We can divide arrays in two categories.

• One-dimensional array (Or single-dimensional array)
• Multi-dimensional array

Why we need arrays?

Let us understand the significance of arrays through an example.

Suppose, I asked you to write a program to input 1000 students marks from user. Finally print average of their marks .

To solve the problem you will declare 1000 integer variable to input marks. Call I/O functions to input marks in 1000 variables and finally find the average.

Think for a while how tedious will be to code if solved using above approach. Declare 1000 variables, take input in all variables, then find average and finally print its average. The above increases length of code, complexity and degrades performance. If you don’t believe, try to code solution using above approach.

To solve above problem efficiently we use arrays. Arrays are good at handling collection of data (collection of 1000 student marks). Mind that in programming, we will always use some data structure (array in our case) to handle a collection of data efficiently.

How to use arrays?

Array in memory is stored as a continuous sequence of bytes. Like variables we give name to an array. However unlike variables, arrays are multi-valued they contain multiple values. Hence you cannot access specific array element directly.

For example, you can write sum = 432; to access sum . But, you cannot access specific array element directly by using array variable name. You cannot write marks to access 4 th student marks.

In array, we use an integer value called index to refer at any element of array. Array index starts from 0 and goes till N - 1 (where N is size of the array). In above case array index ranges from 0 to 4 .

To access individual array element we use array variable name with index enclosed within square brackets [ and ] . To access first element of marks array, we use marks[0] . Similarly to access third element we use marks[2] .

How to declare an array?

Syntax to declare an array.

• data_type is a valid C data type that must be common to all array elements.
• array_name is name given to array and must be a valid C identifier .
• SIZE is a constant value that defines array maximum capacity.

Example to declare an array

How to initialize an array.

There are two ways to initialize an array.

• Static array initialization – Initializes all elements of array during its declaration.
• Dynamic array initialization – The declared array is initialized some time later during execution of program.

Static initialization of array

We define value of all array elements within a pair of curly braces { and } during its declaration. Values are separated using comma , and must be of same type.

Example of static array initialization

Note: Size of array is optional when declaring and initializing array at once. The C compiler automatically determines array size using number of array elements. Hence, you can write above array initialization as.

Dynamic initialization of array

You can assign values to an array element dynamically during execution of program. First declare array with a fixed size. Then use the following syntax to assign values to an element dynamically.

Example to initialize an array dynamically

Instead of hard-coding marks values, you can ask user to input values to array using scanf() function.

The array index is an integer value, so instead of hard-coding you can wrap array input code inside a loop .

The above code will run 5 times from 0 to 4 . In each iteration it ask user to input an integer and stores it in successive elements of marks array.

Example program to implement one-dimensional array

Let us write a C program to declare an array capable of storing 10 student marks. Input marks of all 10 students and find their average.

Output –

Array best practices

• Arrays are fixed size, hence always be cautious while accessing arrays. Accessing an element that does not exists is undefined. You may get a valid value or the program may crash.For example, consider the below program. int array[5]; // Declare an integer array of size 5 /* Accessing sixth element of array which is undefined. */ array[5] = 50; /* Accessing -1th element of array is undefined */ array[-1] = 10;
• Always keep in mind that all array element store a value of similar type.

Recommended array example programs

• Program to read and print array element.
• Program to find maximum and minimum element in array.
• Program to insert a new element in array.
• Program to search an element in array.
• Program to sort array elements.

Practice more array programming exercises to learn more.

Stack Exchange Network

Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Why does C not support direct array assignment?

In C you cannot assign arrays directly.

At first I thought this might because the C facilities were supposed to be implementable with a single or a few instructions and more complicated functionality was offloaded to standard library functions. After all using memcpy() is not that hard. However, one can directly assign structures/unions which can be arbitrarily sized, and can even contain arrays.

What is/was the reasoning for allowing structures/unions to be directly assigned but not arrays, if the former can contain arrays anyway? We can only assign arrays directly if they are wrapped in a structure/union, so my aforementioned hypothesis as to why this is the case is out.

• Because language features are unimplemented by default . –  Doc Brown Commented May 4, 2023 at 5:59

2 Answers 2

It is arguably a shortcoming, due to missing features around arrays, but one the original designers choose not to resolve.  Add in the (over) emphasis on pointers and pointer arithmetic and keeping track of these things yourself as would be done in assembly.

Arrays in C don't really have sizes.  Yes, you can int A[100]; ... sizeof(A) ... for a declared array, but once A is used in an expression, its type is immediately converted to pointer to element (here int* ) and the original array's size is lost.  This is particularly evident with parameters where an array is passed.

There's not even a convenient built-in for length (e.g. say, lengthof ) that would work for arrays of any element size — instead we have to write something like (sizeof(A)/sizeof(*A)) .

A lot of code in C relies on use of pointers where length is kept by the program using other variables or knowledge rather than having the language keep track.

Often, declaring an array in a struct/union as a last member is secret code for variable length.  See for example:

I can't say for sure but apparently resolving the short comings only for declared arrays but not for pointers seemed not all that useful.  So, some larger built in length mechanism would have been required for general use with pointers.

Still, something could have been done, say by having some syntax that allows the user to specify a number of elements — like A = B[0:n] or A[0:n] = B or some other variant — but they simply stopped short of that, leaving it for memcpy and memmove .  Let's also note that when you choose between memcpy and memmove , with the former you're saying that the source and destination do not overlap, whereas with memmove you're saying they might overlap so backwards copying of the elements may be better than forwards (and it will check at runtime).

So, the various problems:

• pointer oriented rather than array oriented
• no implicit size information on pointers
• aliasing issues
• fixed sized arrays are only useful in narrow contexts

I think punting to the standard library was pretty reasonable here, plus as you note for fixed sized arrays, we can wrap them in a struct/union..

C originally came from a predecessor language called B, made by Ken Thompson . In B, there were no types. Everything was a "word" (basically, an int ).

In B, arrays were just pointers to the first element. If you declared an array:

This would allocate 10 words on the stack (to be freed automatically when the function returned, thus auto ), and arr would be a pointer to the first one.

When the type system was added, Dennis Ritchie didn't want any existing code to break. This is why, for example, on early versions of C if you omitted the type it would default to int . It's also where pointer decay (array arguments to functions being just pointers) came from.

For this reason, arrays ended up being a second-class citizen in C for a long time. Because of the stability of the language, even the more modern C standards (like C23 which is supposed to come out this year) have to try to fix it without breaking anything, and this particular issue (copying arrays) is not really a priority, because you rarely actually want to copy an array (especially a large one).

Source: The Development of the C language

Your Answer

Reminder: Answers generated by artificial intelligence tools are not allowed on Software Engineering Stack Exchange. Learn more

Sign up or log in

Post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Not the answer you're looking for? Browse other questions tagged c array unions struct or ask your own question .

• Featured on Meta
• Upcoming sign-up experiments related to tags

Hot Network Questions

• Composition of vectorvalued functions
• Is parapsychology a science?
• I feel like doing a PhD is my only option but I am not excited about it. What can I do to fix my life?
• Freezing Meat in Butcher Paper
• Can I remove an appimage file?
• Audio amplifier for school project
• Is "Shopping malls are a posh place" grammatical when "malls" is a plural and "place" is a singular?
• Why was the 1540 a computer in its own right?
• Parts of Humans
• How to get a listing and other content in a table to align to the top?
• Is there a way knowledge checks can be done without an Intelligence trait?
• Unsure whether to begin a PhD program
• I will not raise my voice to him ever again
• What was God's original plan for humanity prior to the fall?
• Okular window not opening
• Looking at buying house with mechanical septic system. What questions should I be asking?
• Why is nonzero net charge density incompatible with the cosmological principle?
• 70's-80's sci-fi/fantasy movie (TV) with togas and crystals
• How to not make my series repetitive?
• Will a rack-mounted child seat be safe if the rack's maximum load is 2kg less than the seat manufacturer describes as the minimum load?
• Why are worldships not shaped like worlds?
• Roadmap for self study in philosophy
• why std::is_same<int, *(int*)>::value is false?
• Eye Spy: Where are the other two (of six) vehicles docked to the ISS in this Maxar image (& what are they?)

Next: Enumeration Types , Previous: Structures , Up: Top   [ Contents ][ Index ]

An array is a data object that holds a series of elements , all of the same data type. Each element is identified by its numeric index within the array.

We presented arrays of numbers in the sample programs early in this manual (see Array Example ). However, arrays can have elements of any data type, including pointers, structures, unions, and other arrays.

If you know another programming language, you may suppose that you know all about arrays, but C arrays have special quirks, so in this chapter we collect all the information about arrays in C.

The elements of a C array are allocated consecutively in memory, with no gaps between them. Each element is aligned as required for its data type (see Type Alignment ).

C Functions

C structures, c reference.

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.

To create an array, define the data type (like int ) and specify the name of the array followed by square brackets [] .

To insert values to it, use a comma-separated list, inside curly braces:

We have now created a variable that holds an array of four integers.

Access the Elements of an Array

To access an array element, refer to its index number .

Array indexes start with 0 : [0] is the first element. [1] is the second element, etc.

This statement accesses the value of the first element [0] in myNumbers :

Change an Array Element

To change the value of a specific element, refer to the index number:

Loop Through an Array

You can loop through the array elements with the for loop.

The following example outputs all elements in the myNumbers array:

Set Array Size

Another common way to create arrays, is to specify the size of the array, and add elements later:

Using this method, you should know the number of array elements in advance, in order for the program to store enough memory.

You are not able to change the size of the array after creation.

C Exercises

Test yourself with exercises.

Create an array of type int called myNumbers .

Start the Exercise

COLOR PICKER

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: [email protected]

Report Error

If you want to report an error, or if you want to make a suggestion, send us an e-mail: [email protected]

Top Tutorials

Top references, top examples, get certified.

cppreference.com

Array declaration.

Declares an object of array type.

[ edit ] Syntax

An array declaration is any simple declaration whose declarator has the form

A declaration of the form T a [ N ] ; , declares a as an array object that consists of N contiguously allocated objects of type T . The elements of an array are numbered ​ 0 ​ , …, N - 1 , and may be accessed with the subscript operator [] , as in a [ 0 ] , …, a [ N - 1 ] .

Arrays can be constructed from any fundamental type (except void ), pointers , pointers to members , classes , enumerations , or from other arrays of known bound (in which case the array is said to be multi-dimensional). In other words, only object types except for array types of unknown bound can be element types of array types. Array types of incomplete element type are also incomplete types.

There are no arrays of references or arrays of functions.

Applying cv-qualifiers to an array type (through typedef or template type manipulation) applies the qualifiers to the element type, but any array type whose elements are of cv-qualified type is considered to have the same cv-qualification.

When used with new[]-expression , the size of an array may be zero; such an array has no elements:

[ edit ] Assignment

Objects of array type cannot be modified as a whole: even though they are lvalues (e.g. an address of array can be taken), they cannot appear on the left hand side of an assignment operator:

[ edit ] Array-to-pointer decay

There is an implicit conversion from lvalues and rvalues of array type to rvalues of pointer type: it constructs a pointer to the first element of an array. This conversion is used whenever arrays appear in context where arrays are not expected, but pointers are:

[ edit ] Multidimensional arrays

When the element type of an array is another array, it is said that the array is multidimensional:

Note that when array-to-pointer decay is applied, a multidimensional array is converted to a pointer to its first element (e.g., a pointer to its first row or to its first plane): array-to-pointer decay is applied only once.

[ edit ] Arrays of unknown bound

If expr is omitted in the declaration of an array, the type declared is "array of unknown bound of T", which is a kind of incomplete type , except when used in a declaration with an aggregate initializer :

Because array elements cannot be arrays of unknown bound, multidimensional arrays cannot have unknown bound in a dimension other than the first:

If there is a preceding declaration of the entity in the same scope in which the bound was specified, an omitted array bound is taken to be the same as in that earlier declaration, and similarly for the definition of a static data member of a class:

References and pointers to arrays of unknown bound can be formed, but cannot (until C++20) and can (since C++20) be initialized or assigned from arrays and pointers to arrays of known bound. Note that in the C programming language, pointers to arrays of unknown bound are compatible with pointers to arrays of known bound and are thus convertible and assignable in both directions.

Pointers to arrays of unknown bound cannot participate in pointer arithmetic and cannot be used on the left of the subscript operator , but can be dereferenced.

[ edit ] Array rvalues

Although arrays cannot be returned from functions by value and cannot be targets of most cast expressions, array prvalues may be formed by using a type alias to construct an array temporary using brace-initialized functional cast .

Array xvalues may be formed directly by accessing an array member of a class rvalue or by using std::move or another cast or function call that returns an rvalue reference.

[ edit ] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[ edit ] See also

• Recent changes
• Offline version
• What links here
• Related changes
• Upload file
• Special pages
• Printable version
• Permanent link
• Page information
• In other languages
• This page was last modified on 4 April 2024, at 07:41.
• This page has been accessed 365,986 times.
• Privacy policy
• About cppreference.com
• Disclaimers

• C Programming Tutorial
• C - Overview
• C - Features
• C - History
• C - Environment Setup
• C - Program Structure
• C - Hello World
• C - Compilation Process
• C - Comments
• C - Keywords
• C - Identifiers
• C - User Input
• C - Basic Syntax
• C - Data Types
• C - Variables
• C - Integer Promotions
• C - Type Conversion
• C - Booleans
• C - Constants
• C - Literals
• C - Escape sequences
• C - Format Specifiers
• C - Storage Classes
• C - Operators
• C - Arithmetic Operators
• C - Relational Operators
• C - Logical Operators
• C - Bitwise Operators
• C - Assignment Operators
• C - Unary Operators
• C - Increment and Decrement Operators
• C - Ternary Operator
• C - sizeof Operator
• C - Operator Precedence
• C - Misc Operators
• C - Decision Making
• C - if statement
• C - if...else statement
• C - nested if statements
• C - switch statement
• C - nested switch statements
• C - While loop
• C - For loop
• C - Do...while loop
• C - Nested loop
• C - Infinite loop
• C - Break Statement
• C - Continue Statement
• C - goto Statement
• C - Functions
• C - Main Functions
• C - Function call by Value
• C - Function call by reference
• C - Nested Functions
• C - Variadic Functions
• C - User-Defined Functions
• C - Callback Function
• C - Return Statement
• C - Recursion
• C - Scope Rules
• C - Static Variables
• C - Global Variables
• C - Properties of Array
• C - Multi-Dimensional Arrays
• C - Passing Arrays to Function
• C - Return Array from Function
• C - Variable Length Arrays
• C - Pointers
• C - Pointers and Arrays
• C - Applications of Pointers
• C - Pointer Arithmetics
• C - Array of Pointers
• C - Pointer to Pointer
• C - Passing Pointers to Functions
• C - Return Pointer from Functions
• C - Function Pointers
• C - Pointer to an Array
• C - Pointers to Structures
• C - Chain of Pointers
• C - Pointer vs Array
• C - Character Pointers and Functions
• C - NULL Pointer
• C - void Pointer
• C - Dangling Pointers
• C - Dereference Pointer
• C - Near, Far and Huge Pointers
• C - Initialization of Pointer Arrays
• C - Pointers vs. Multi-dimensional Arrays
• C - Strings
• C - Array of Strings
• C - Special Characters
• C - Structures
• C - Structures and Functions
• C - Arrays of Structures
• C - Self-Referential Structures
• C - Lookup Tables
• C - Dot (.) Operator
• C - Enumeration (or enum)
• C - Nested Structures
• C - Structure Padding and Packing
• C - Anonymous Structure and Union
• C - Bit Fields
• C - Typedef
• C - Input & Output
• C - File I/O
• C - Preprocessors
• C - Pragmas
• C - Preprocessor Operators
• C - Header Files
• C - Type Casting
• C - Error Handling
• C - Variable Arguments
• C - Memory Management
• C - Command Line Arguments
• C Programming Resources
• C - Questions & Answers
• C - Quick Guide
• C - Useful Resources
• C - Discussion
• Selected Reading
• UPSC IAS Exams Notes
• Developer's Best Practices
• Questions and Answers
• Effective Resume Writing
• HR Interview Questions
• Computer Glossary

Pointer to an Array in C

An array name is a constant pointer to the first element of the array. Therefore, in this declaration,

balance is a pointer to &balance[0] , which is the address of the first element of the array.

In this code, we have a pointer ptr that points to the address of the first element of an integer array called balance .

In all the three cases, you get the same output −

If you fetch the value stored at the address that ptr points to, that is *ptr , then it will return 1 .

Array Names as Constant Pointers

It is legal to use array names as constant pointers and vice versa. Therefore, *(balance + 4) is a legitimate way of accessing the data at balance[4] .

Once you store the address of the first element in " ptr ", you can access the array elements using *ptr , *(ptr + 1) , *(ptr + 2) , and so on.

The following example demonstrates all the concepts discussed above −

When you run this code, it will produce the following output −

In the above example, ptr is a pointer that can store the address of a variable of double type. Once we have the address in ptr , *ptr will give us the value available at the address stored in ptr .

To Continue Learning Please Login

• Skip to main content
• Skip to search
• Skip to select language
• Sign up for free
• Português (do Brasil)

Indexed collections

This chapter introduces collections of data which are ordered by an index value. This includes arrays and array-like constructs such as Array objects and TypedArray objects.

An array is an ordered list of values that you refer to with a name and an index.

For example, consider an array called emp , which contains employees' names indexed by their numerical employee number. So emp[0] would be employee number zero, emp[1] employee number one, and so on.

JavaScript does not have an explicit array data type. However, you can use the predefined Array object and its methods to work with arrays in your applications. The Array object has methods for manipulating arrays in various ways, such as joining, reversing, and sorting them. It has a property for determining the array length and other properties for use with regular expressions.

We will be focusing on arrays in this article, but many of the same concepts apply to typed arrays as well, since arrays and typed arrays share many similar methods. For more information on typed arrays, see the typed array guide .

Creating an array

The following statements create equivalent arrays:

element0, element1, …, elementN is a list of values for the array's elements. When these values are specified, the array is initialized with them as the array's elements. The array's length property is set to the number of arguments.

The bracket syntax is called an "array literal" or "array initializer." It's shorter than other forms of array creation, and so is generally preferred. See Array literals for details.

To create an array with non-zero length, but without any items, either of the following can be used:

Note: In the above code, arrayLength must be a Number . Otherwise, an array with a single element (the provided value) will be created. Calling arr.length will return arrayLength , but the array doesn't contain any elements. A for...in loop will not find any property on the array.

In addition to a newly defined variable as shown above, arrays can also be assigned as a property of a new or an existing object:

If you wish to initialize an array with a single element, and the element happens to be a Number , you must use the bracket syntax. When a single Number value is passed to the Array() constructor or function, it is interpreted as an arrayLength , not as a single element.

This creates an array with only one element: the number 42.

This creates an array with no elements and arr.length set to 42.

This is equivalent to:

Calling Array(N) results in a RangeError , if N is a non-whole number whose fractional portion is non-zero. The following example illustrates this behavior.

If your code needs to create arrays with single elements of an arbitrary data type, it is safer to use array literals. Alternatively, create an empty array first before adding the single element to it.

You can also use the Array.of static method to create arrays with single element.

Referring to array elements

Because elements are also properties, you can access them using property accessors . Suppose you define the following array:

You can refer to the first element of the array as myArray[0] , the second element of the array as myArray[1] , etc… The index of the elements begins with zero.

Note: You can also use property accessors to access other properties of the array, like with an object.

Populating an array

You can populate an array by assigning values to its elements. For example:

Note: If you supply a non-integer value to the array operator in the code above, a property will be created in the object representing the array, instead of an array element.

You can also populate an array when you create it:

Understanding length

At the implementation level, JavaScript's arrays actually store their elements as standard object properties, using the array index as the property name.

The length property is special. Its value is always a positive integer greater than the index of the last element if one exists. (In the example below, 'Dusty' is indexed at 30 , so cats.length returns 30 + 1 ).

Remember, JavaScript Array indexes are 0-based: they start at 0 , not 1 . This means that the length property will be one more than the highest index stored in the array:

You can also assign to the length property.

Writing a value that is shorter than the number of stored items truncates the array. Writing 0 empties it entirely:

Iterating over arrays

A common operation is to iterate over the values of an array, processing each one in some way. The simplest way to do this is as follows:

If you know that none of the elements in your array evaluate to false in a boolean context—if your array consists only of DOM nodes, for example—you can use a more efficient idiom:

This avoids the overhead of checking the length of the array, and ensures that the div variable is reassigned to the current item each time around the loop for added convenience.

The forEach() method provides another way of iterating over an array:

The function passed to forEach is executed once for every item in the array, with the array item passed as the argument to the function. Unassigned values are not iterated in a forEach loop.

Note that the elements of an array that are omitted when the array is defined are not listed when iterating by forEach , but are listed when undefined has been manually assigned to the element:

Since JavaScript array elements are saved as standard object properties, it is not advisable to iterate through JavaScript arrays using for...in loops, because normal elements and all enumerable properties will be listed.

Array methods

The Array object has the following methods:

The concat() method joins two or more arrays and returns a new array.

The join() method joins all elements of an array into a string.

The push() method adds one or more elements to the end of an array and returns the resulting length of the array.

The pop() method removes the last element from an array and returns that element.

The shift() method removes the first element from an array and returns that element.

The unshift() method adds one or more elements to the front of an array and returns the new length of the array.

The slice() method extracts a section of an array and returns a new array.

The at() method returns the element at the specified index in the array, or undefined if the index is out of range. It's notably used for negative indices that access elements from the end of the array.

The splice() method removes elements from an array and (optionally) replaces them. It returns the items which were removed from the array.

The reverse() method transposes the elements of an array, in place: the first array element becomes the last and the last becomes the first. It returns a reference to the array.

The flat() method returns a new array with all sub-array elements concatenated into it recursively up to the specified depth.

The sort() method sorts the elements of an array in place, and returns a reference to the array.

sort() can also take a callback function to determine how array elements are compared. The callback function is called with two arguments, which are two values from the array. The function compares these two values and returns a positive number, negative number, or zero, indicating the order of the two values. For instance, the following will sort the array by the last letter of a string:

• if a is less than b by the sorting system, return -1 (or any negative number)
• if a is greater than b by the sorting system, return 1 (or any positive number)
• if a and b are considered equivalent, return 0 .

The indexOf() method searches the array for searchElement and returns the index of the first match.

The lastIndexOf() method works like indexOf , but starts at the end and searches backwards.

The forEach() method executes callback on every array item and returns undefined .

The forEach method (and others below) that take a callback are known as iterative methods , because they iterate over the entire array in some fashion. Each one takes an optional second argument called thisArg . If provided, thisArg becomes the value of the this keyword inside the body of the callback function. If not provided, as with other cases where a function is invoked outside of an explicit object context, this will refer to the global object ( window , globalThis , etc.) when the function is not strict , or undefined when the function is strict.

Note: The sort() method introduced above is not an iterative method, because its callback function is only used for comparison and may not be called in any particular order based on element order. sort() does not accept the thisArg parameter either.

The map() method returns a new array of the return value from executing callback on every array item.

The flatMap() method runs map() followed by a flat() of depth 1.

The filter() method returns a new array containing the items for which callback returned true .

The find() method returns the first item for which callback returned true .

The findLast() method returns the last item for which callback returned true .

The findIndex() method returns the index of the first item for which callback returned true .

The findLastIndex() method returns the index of the last item for which callback returned true .

The every() method returns true if callback returns true for every item in the array.

The some() method returns true if callback returns true for at least one item in the array.

The reduce() method applies callback(accumulator, currentValue, currentIndex, array) for each value in the array for the purpose of reducing the list of items down to a single value. The reduce function returns the final value returned by callback function.

If initialValue is specified, then callback is called with initialValue as the first parameter value and the value of the first item in the array as the second parameter value.

If initialValue is not specified, then callback 's first two parameter values will be the first and second elements of the array. On every subsequent call, the first parameter's value will be whatever callback returned on the previous call, and the second parameter's value will be the next value in the array.

If callback needs access to the index of the item being processed, or access to the entire array, they are available as optional parameters.

The reduceRight() method works like reduce() , but starts with the last element.

reduce and reduceRight are the least obvious of the iterative array methods. They should be used for algorithms that combine two values recursively in order to reduce a sequence down to a single value.

Array transformations

You can transform back and forth between arrays and other data structures.

Grouping the elements of an array

The Object.groupBy() method can be used to group the elements of an array, using a test function that returns a string indicating the group of the current element.

Here we have a simple inventory array that contains "food" objects that have a name and a type .

To use Object.groupBy() , you supply a callback function that is called with the current element, and optionally the current index and array, and returns a string indicating the group of the element.

The code below uses an arrow function to return the type of each array element (this uses object destructuring syntax for function arguments to unpack the type element from the passed object). The result is an object that has properties named after the unique strings returned by the callback. Each property is assigned an array containing the elements in the group.

Note that the returned object references the same elements as the original array (not deep copies ). Changing the internal structure of these elements will be reflected in both the original array and the returned object.

If you can't use a string as the key, for example, if the information to group is associated with an object that might change, then you can instead use Map.groupBy() . This is very similar to Object.groupBy() except that it groups the elements of the array into a Map that can use an arbitrary value ( object or primitive ) as a key.

Sparse arrays

Arrays can contain "empty slots", which are not the same as slots filled with the value undefined . Empty slots can be created in one of the following ways:

In some operations, empty slots behave as if they are filled with undefined .

But in others (most notably array iteration methods), empty slots are skipped.

For a complete list of how array methods behave with sparse arrays, see the Array reference page .

Multi-dimensional arrays

Arrays can be nested, meaning that an array can contain another array as an element. Using this characteristic of JavaScript arrays, multi-dimensional arrays can be created.

The following code creates a two-dimensional array.

This example creates an array with the following rows:

Using arrays to store other properties

Arrays can also be used like objects, to store related information.

For example, when an array is the result of a match between a regular expression and a string, the array returns properties and elements that provide information about the match. An array is the return value of RegExp.prototype.exec() , String.prototype.match() , and String.prototype.split() . For information on using arrays with regular expressions, see Regular Expressions .

Working with array-like objects

Some JavaScript objects, such as the NodeList returned by document.getElementsByTagName() or the arguments object made available within the body of a function, look and behave like arrays on the surface but do not share all of their methods. The arguments object provides a length attribute but does not implement array methods like forEach() .

Array methods cannot be called directly on array-like objects.

But you can call them indirectly using Function.prototype.call() .

Array prototype methods can be used on strings as well, since they provide sequential access to their characters in a similar way to arrays:

SORT function

The SORT function sorts the contents of a range or array. 

In this example, we're sorting by Region, Sales Rep, and Product individually with =SORT(A2:A17), copied across cells F2, H2, and J2.

SORT returns a sorted array of the elements in an array. The returned array is the same shape as the provided array argument. 

=SORT(array,[sort_index],[sort_order],[by_col])

Where sort_index is not provided, row1/col1 will be presumed. Where order is not provided, ascending order will be presumed. By default Excel will sort by row, and will only sort by column where by_col is TRUE. When by_col is FALSE or missing Excel will sort by row.

The SORT function is provided to sort data in an array. If you want to sort data in the grid, it's better to use the SORTBY function , as it is more flexible. SORTBY will respect column additions/deletions, because it references a range, where SORT references a column index number.

An array can be thought of as a row of values, a column of values, or a combination of rows and columns of values. In the example above, the source array for our SORT formula is range A5:D20.

The SORT function will return an array, which will spill if it's the final result of a formula. This means that Excel will dynamically create the appropriate sized array range when you press ENTER . If your supporting data is in an Excel Table , then the array will automatically resize as you add or remove data from your array range if you're using Structured References . For more details see this article on Spilled Array Behavior .

Excel has limited support for dynamic arrays between workbooks, and this scenario is only supported when both workbooks are open. If you close the source workbook, any linked dynamic array formulas will return a #REF! error when they are refreshed.

Sort a range of values in descending order.

Use SORT and FILTER together to sort a range in ascending order, and limit it to values over 5,000.

Need more help?

You can always ask an expert in the Excel Tech Community  or get support in  Communities .

FILTER function

RANDARRAY function

SEQUENCE function

SORTBY function

UNIQUE function

#SPILL! errors in Excel

Dynamic arrays and spilled array behavior

Implicit intersection operator: @

Want more options?

Explore subscription benefits, browse training courses, learn how to secure your device, and more.

Microsoft 365 subscription benefits

Microsoft 365 training

Microsoft security

Accessibility center

Communities help you ask and answer questions, give feedback, and hear from experts with rich knowledge.

Ask the Microsoft Community

Microsoft Tech Community

Windows Insiders

Microsoft 365 Insiders

Was this information helpful?

Thank you for your feedback.

The N-dimensional array ( ndarray ) #

An ndarray is a (usually fixed-size) multidimensional container of items of the same type and size. The number of dimensions and items in an array is defined by its shape , which is a tuple of N non-negative integers that specify the sizes of each dimension. The type of items in the array is specified by a separate data-type object (dtype) , one of which is associated with each ndarray.

As with other container objects in Python, the contents of an ndarray can be accessed and modified by indexing or slicing the array (using, for example, N integers), and via the methods and attributes of the ndarray .

Different ndarrays can share the same data, so that changes made in one ndarray may be visible in another. That is, an ndarray can be a “view” to another ndarray, and the data it is referring to is taken care of by the “base” ndarray. ndarrays can also be views to memory owned by Python strings or objects implementing the buffer or array interfaces.

A 2-dimensional array of size 2 x 3, composed of 4-byte integer elements:

The array can be indexed using Python container-like syntax:

For example slicing can produce views of the array:

Constructing arrays #

New arrays can be constructed using the routines detailed in Array creation routines , and also by using the low-level ndarray constructor:

Indexing arrays #

Arrays can be indexed using an extended Python slicing syntax, array[selection] . Similar syntax is also used for accessing fields in a structured data type .

Array Indexing .

Internal memory layout of an ndarray #

An instance of class ndarray consists of a contiguous one-dimensional segment of computer memory (owned by the array, or by some other object), combined with an indexing scheme that maps N integers into the location of an item in the block. The ranges in which the indices can vary is specified by the shape of the array. How many bytes each item takes and how the bytes are interpreted is defined by the data-type object associated with the array.

A segment of memory is inherently 1-dimensional, and there are many different schemes for arranging the items of an N -dimensional array in a 1-dimensional block. NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme . In a strided scheme, the N-dimensional index \((n_0, n_1, ..., n_{N-1})\) corresponds to the offset (in bytes):

from the beginning of the memory block associated with the array. Here, \(s_k\) are integers which specify the strides of the array. The column-major order (used, for example, in the Fortran language and in Matlab ) and row-major order (used in C) schemes are just specific kinds of strided scheme, and correspond to memory that can be addressed by the strides:

where \(d_j\) = self.shape[j] .

Both the C and Fortran orders are contiguous , i.e., single-segment, memory layouts, in which every part of the memory block can be accessed by some combination of the indices.

Contiguous arrays and single-segment arrays are synonymous and are used interchangeably throughout the documentation.

While a C-style and Fortran-style contiguous array, which has the corresponding flags set, can be addressed with the above strides, the actual strides may be different. This can happen in two cases:

If self.shape[k] == 1 then for any legal index index[k] == 0 . This means that in the formula for the offset \(n_k = 0\) and thus \(s_k n_k = 0\) and the value of \(s_k\) = self.strides[k] is arbitrary. If an array has no elements ( self.size == 0 ) there is no legal index and the strides are never used. Any array with no elements may be considered C-style and Fortran-style contiguous.

Point 1. means that self and self.squeeze() always have the same contiguity and aligned flags value. This also means that even a high dimensional array could be C-style and Fortran-style contiguous at the same time.

An array is considered aligned if the memory offsets for all elements and the base offset itself is a multiple of self.itemsize . Understanding memory-alignment leads to better performance on most hardware.

It does not generally hold that self.strides[-1] == self.itemsize for C-style contiguous arrays or self.strides[0] == self.itemsize for Fortran-style contiguous arrays is true.

NPY_RELAXED_STRIDES_DEBUG=1 can be used to help find errors when incorrectly relying on the strides in C-extension code (see below warning).

Data in new ndarrays is in the row-major (C) order, unless otherwise specified, but, for example, basic array slicing often produces views in a different scheme.

Several algorithms in NumPy work on arbitrarily strided arrays. However, some algorithms require single-segment arrays. When an irregularly strided array is passed in to such algorithms, a copy is automatically made.

Array attributes #

Array attributes reflect information that is intrinsic to the array itself. Generally, accessing an array through its attributes allows you to get and sometimes set intrinsic properties of the array without creating a new array. The exposed attributes are the core parts of an array and only some of them can be reset meaningfully without creating a new array. Information on each attribute is given below.

Memory layout #

The following attributes contain information about the memory layout of the array:

Data type #

Data type objects

The data type object associated with the array can be found in the dtype attribute:

Other attributes #

Array interface #

The array interface protocol .

ctypes foreign function interface #

Array methods #

An ndarray object has many methods which operate on or with the array in some fashion, typically returning an array result. These methods are briefly explained below. (Each method’s docstring has a more complete description.)

For the following methods there are also corresponding functions in numpy : all , any , argmax , argmin , argpartition , argsort , choose , clip , compress , copy , cumprod , cumsum , diagonal , imag , max , mean , min , nonzero , partition , prod , ptp , put , ravel , real , repeat , reshape , round , searchsorted , sort , squeeze , std , sum , swapaxes , take , trace , transpose , var .

Array conversion #

Shape manipulation #

For reshape, resize, and transpose, the single tuple argument may be replaced with n integers which will be interpreted as an n-tuple.

Item selection and manipulation #

For array methods that take an axis keyword, it defaults to None . If axis is None , then the array is treated as a 1-D array. Any other value for axis represents the dimension along which the operation should proceed.

Calculation #

Many of these methods take an argument named axis . In such cases,

If axis is None (the default), the array is treated as a 1-D array and the operation is performed over the entire array. This behavior is also the default if self is a 0-dimensional array or array scalar. (An array scalar is an instance of the types/classes float32, float64, etc., whereas a 0-dimensional array is an ndarray instance containing precisely one array scalar.)

If axis is an integer, then the operation is done over the given axis (for each 1-D subarray that can be created along the given axis).

Example of the axis argument

A 3-dimensional array of size 3 x 3 x 3, summed over each of its three axes

The parameter dtype specifies the data type over which a reduction operation (like summing) should take place. The default reduce data type is the same as the data type of self . To avoid overflow, it can be useful to perform the reduction using a larger data type.

For several methods, an optional out argument can also be provided and the result will be placed into the output array given. The out argument must be an ndarray and have the same number of elements. It can have a different data type in which case casting will be performed.

Arithmetic, matrix multiplication, and comparison operations #

Arithmetic and comparison operations on ndarrays are defined as element-wise operations, and generally yield ndarray objects as results.

Each of the arithmetic operations ( + , - , * , / , // , % , divmod() , ** or pow() , << , >> , & , ^ , | , ~ ) and the comparisons ( == , < , > , <= , >= , != ) is equivalent to the corresponding universal function (or ufunc for short) in NumPy. For more information, see the section on Universal Functions .

Comparison operators:

Truth value of an array ( bool() ):

Truth-value testing of an array invokes ndarray.__bool__ , which raises an error if the number of elements in the array is larger than 1, because the truth value of such arrays is ambiguous. Use .any() and .all() instead to be clear about what is meant in such cases. (If the number of elements is 0, the array evaluates to False .)

Unary operations:

Arithmetic:

Any third argument to pow is silently ignored, as the underlying ufunc takes only two arguments.

Because ndarray is a built-in type (written in C), the __r{op}__ special methods are not directly defined.

The functions called to implement many arithmetic special methods for arrays can be modified using __array_ufunc__ .

Arithmetic, in-place:

In place operations will perform the calculation using the precision decided by the data type of the two operands, but will silently downcast the result (if necessary) so it can fit back into the array. Therefore, for mixed precision calculations, A {op}= B can be different than A = A {op} B . For example, suppose a = ones((3,3)) . Then, a += 3j is different than a = a + 3j : while they both perform the same computation, a += 3 casts the result to fit back in a , whereas a = a + 3j re-binds the name a to the result.

Matrix Multiplication:

Matrix operators @ and @= were introduced in Python 3.5 following PEP 465 , and the @ operator has been introduced in NumPy 1.10.0. Further information can be found in the matmul documentation.

Special methods #

For standard library functions:

Basic customization:

Container customization: (see Indexing )

Conversion; the operations int() , float() and complex() . They work only on arrays that have one element in them and return the appropriate scalar.

String representations:

Utility method for typing:

• Stack Overflow Public questions & answers
• Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers
• Talent Build your employer brand
• Advertising Reach developers & technologists worldwide
• Labs The future of collective knowledge sharing
• About the company

Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Get early access and see previews of new features.

C/C++ arrays assignment

Sample code:

Is there any way to init it shorter? Something like:

I don't need solution like:

Definition and initialization must be separate.

• initialization
• variable-assignment

• Terminology: Initialization is giving a value at the moment of definition. What you want is "array assignment". –  Kos Commented Jan 1, 2011 at 22:30

5 Answers 5

What you are asking for cannot be done directly. There are, however different things that you can do there, starting from creation of a local array initialized with the aggregate initialization and then memcpy -ed over your array (valid only for POD types), or using higher level libraries like boost::assign .

I don't have time to check how to do this with boost::assign , as I hardly ever work with raw arrays.

• Thanks. I just thought that exists some way in this language or in compiler extensions. –  kyrylomyr Commented Dec 25, 2010 at 13:13

Arrays can be assigned directly:

Check the C++ Arrays tutorial , too.

• I don't need initialization after definion of array. I need to init array deeper in the code. –  kyrylomyr Commented Dec 25, 2010 at 13:02
• 1 @archer: then why can't you define it at the point you need it to be initialized? –  Yakov Galka Commented Dec 25, 2010 at 13:05
• This point located in the loop. Maybe im mistaken, but with huge amount of loop executes will be more optimized to define array out of this loop. –  kyrylomyr Commented Dec 25, 2010 at 13:08
• 1 You can assign it in the same way: a = {1, 2, 3} . But that's actually C++0x ("extended initializer lists"). If you need to reassign the array in each loop iteration, you can still use memcpy . –  AndiDog Commented Dec 25, 2010 at 13:11
• 2 @archer: then you're almost surely wrong. Array allocation on the stack in just a stack pointer addition/subtraction. The compiler may optimize and allocate it in function's stackframe just like any other variable. –  Yakov Galka Commented Dec 25, 2010 at 13:27

int a[] = {1,2,3};

this doesn't work for you?

• Microsoft C++ (VS2010). You are using initialization after definition. I need separate. –  kyrylomyr Commented Dec 25, 2010 at 13:03
• main with no return type!? What compiler are you using!? –  Yakov Galka Commented Dec 25, 2010 at 13:04
• @ybungalobill: gcc 3.3.5 but the point was not the main but the array use, just put it up quickly :) –  Ass3mbler Commented Dec 25, 2010 at 13:08

What about the C99 array initialization?

• Thanks for mentioning this, but we're not discussing initialization :) –  Kos Commented Jan 1, 2011 at 22:29

Your Answer

Reminder: Answers generated by artificial intelligence tools are not allowed on Stack Overflow. Learn more

Sign up or log in

Post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Not the answer you're looking for? Browse other questions tagged c++ c arrays initialization variable-assignment or ask your own question .

• Featured on Meta
• Upcoming sign-up experiments related to tags
• Policy: Generative AI (e.g., ChatGPT) is banned
• The return of Staging Ground to Stack Overflow
• The 2024 Developer Survey Is Live

Hot Network Questions

• Okular window not opening
• Unsure whether to begin a PhD program
• Roadmap for self study in philosophy
• How can I calculate how much power an isolation transformer itself consumes if no load is provided?
• How would I fix this leaking garage?
• Where in "À la recherche du temps perdu" does the main character indicate that he would be named after the author?
• How are real numbers defined in elementary recursive arithmetic?
• Psychology Today Culture Fair IQ test question
• why std::is_same<int, *(int*)>::value is false?
• Academic Interview Question: "What is the title of your second book?"
• Will a rack-mounted child seat be safe if the rack's maximum load is 2kg less than the seat manufacturer describes as the minimum load?
• Definability properties of box-open subsets of Polish space
• Is parapsychology a science?
• Bizarre integral solved using conservation of energy
• If humans colonized Earth 100,000 years ago, would we know it?
• Meaning of 相 in 讓僑胞擁有與國內民眾相類似之教育資源
• How does gravity overpower a vacuum?
• TCP source port sharing
• Bringing a game console into Saudi Arabia
• I buy retrocomputing devices, but they set my allergies off. Any advice on sanitizing new acquisitions?
• What was God's original plan for humanity prior to the fall?
• What is the time-travel story where "ugly chickens" are trapped in the past and brought to the present to become ingredients for a soup?
• What did Jesus mean about the Temple as the Father's House in John 2:16?
• What is the goal of the message “astronaut use only” written on one Hubble's module?

NDepend Blog

Improve your .NET code quality with NDepend

C# Array and List Fastest Loop in 2024

Share this:.

At NDepend we value your time, so here are our key findings:

• When iterating over a C# array, the foreach way is the quickest.
• In a for loop, storing the array.Length or list.Count in a variable does not improve performance and may actually decrease it.
• for  loop is most efficient on a List<T> than foreach .
• However, the most efficient way to loop over a List<T> involves accessing the internal array via a Span<T> using Span<int> span = CollectionsMarshal.AsSpan(list) . This approach is beneficial in performance-critical situations, provided that no elements are added or removed from the list.
• Using a lambda for iterating the LINQ way, like in Array.Foreach(array, item => ...) or list.ForEach(item => ...) is unsurprisingly , way slower than regular for and foreach loops.

Let’s go through the experiments and investigations that led us to these conclusions:

Array int[] Fastest Loop

Here are the results obtained through 9 ways to loop over an int[] .

Here is the code that you can copy straight into a Program.cs file, assuming the project imports BenchmarkDotNet:

foreach wins, why?

While the foreach loop over an array can sometimes be marginally slower than when using Span<T> , the difference is negligible. Additionally, introducing Span<T> can complicate the code, which may not justify the tiny performance benefit.

However, let’s investigate why foreach is faster than for . Let’s use SharpLab to decompile this program  and investigate:

Here is the result from the C# compiler:

These are quite similar. However the foreach loop introduces a reference to the array as a local variable. This modification enables the JIT compiler to eliminate bounds checking, significantly speeding up each loop. Observe the variations in the generated assembly code. To make it easier to read, the loop is highlighted in both cases.

Managed pointers and the C# keyword ref

The ForSpanRefLoop() and ForSpanRefLoop2() ways are extracted from two Nick Chapsas’ videos here and here . They involve ref variables. In C# the keyword ref means managed pointers . In C# 1.0 the keyword ref was only used for passing parameters by reference. Since C# 7.0 almost every version of C# adds new areas where managed pointers can be used: ref variable, ref return, struct ref …

Managed pointers constitute a unique feature of the .NET runtime that offers considerable benefits:

• They can target various types of memory: local variables, in or out method parameters, stack locations, heap objects, object fields, array elements, strings, string locations, and unmanaged memory buffers.
• The Garbage Collector recognizes managed pointers and adjusts them appropriately when the targeted objects are relocated.
• They function efficiently.

The main restriction is that managed pointers must remain on the thread stack. This restriction also makes them faster than usual .NET references since the location of a managed pointer cannot change during a GC operation.

Span<T> implementation is based on managed pointers. All in all, Span<T> is a way to work with pointers like in C, in a safe context even though calls to method like Unsafe.Add() makes the code, well, unsafe.

While Span<T> doesn’t help improve performance when looping over an array, we’ll see that it is valuable when looping over a List<T> .

References:

• Managed pointers, Span, ref struct, C#11 ref fields and the scoped keyword
• Improve C# code performance with Span<T>

List<T> Fastest Loop

We slightly modified the program above to make it work on a List<int> . Here are the results:

Array vs. List Loop

First, let’s compare array and list results. Looping over a list is generally slower than looping over an array. This makes sense since List<T> internally holds a T[] . Thus, it necessarily adds a layer of complexity.

Span<T> makes list loops faster

The real surprise is that using a Span<T> to loop over a list is significantly faster than for and foreach regular ways. What happens is that the call to CollectionsMarshal.AsSpan(list) obtains a managed pointer to the list’s internal array. This call is generally a bad idea because if some elements are added or removed, the list might internally allocate a new array. Thus the span obtained now points toward void memory. This is demonstrated by this program:

However, assuming that the number of elements in the list and its capacity doesn’t get modified, using CollectionsMarshal.AsSpan(list) does help improve the performance of looping over a list in critical scenarios.

for loop is faster on list than foreach

Unlike array, for loops are faster on lists than foreach loop. The reason is obvious when investigating this program in SharpLap :

The C# compiler produces this code. The call to enumerator.MoveNext() and the try/catch block necessarily degrade the performances:

We listed the key findings in the introduction. Let’s conclude that future versions of .NET and C# might change these results. For example, in the future, the C# compiler might assert that a list doesn’t get modified and use the Span<T> based optimization. We will update this post regularly to find out.

As passionate programmers, we find all these insights intriguing. However, it’s important to remember that in most scenarios, code readability outweighs the benefits of minor performance enhancements . Therefore, let’s reserve the use of MemoryMarshal , CollectionsMarshal , and Unsafe stuff for those parts of the code where performance is absolutely critical.

Make your .NET code beautiful with NDepend

Download the NDepend Trial and gain valuable insights into your .NET code within a few minutes

Forward this article to the Sonar folks. It’s constantly yelling to use linq versus a foreach, despite ther performance hit. This making code reviews… slower.

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Notify me of follow-up comments by email.

Notify me of new posts by email.

• Practice Searching Algorithms
• MCQs on Searching Algorithms
• Tutorial on Searching Algorithms
• Linear Search
• Binary Search
• Ternary Search
• Jump Search
• Sentinel Linear Search
• Interpolation Search
• Exponential Search
• Fibonacci Search
• Ubiquitous Binary Search
• Linear Search Vs Binary Search
• Interpolation Search Vs Binary Search
• Binary Search Vs Ternary Search
• Sentinel Linear Search Vs Linear Search
• Searching Algorithms

Most Common Searching Algorithms

• Introduction to Linear Search Algorithm
• Binary Search Algorithm - Iterative and Recursive Implementation

Other Searching Algorithms

• Meta Binary Search | One-Sided Binary Search
• The Ubiquitous Binary Search | Set 1

Comparisons between Searching Algorithms

• Linear Search vs Binary Search
• Interpolation search vs Binary search
• Why is Binary Search preferred over Ternary Search?
• Is Sentinel Linear Search better than normal Linear Search?

Library implementations of Searching algorithms

• Binary Search functions in C++ STL (binary_search, lower_bound and upper_bound)
• Arrays.binarySearch() in Java with examples | Set 1
• Arrays.binarySearch() in Java with examples | Set 2 (Search in subarray)
• Collections.binarySearch() in Java with Examples

Easy problems on Searching algorithms

• Find the Missing Number
• Find the first repeating element in an array of integers
• Find the missing and repeating number
• Count 1's in a sorted binary array
• Sum of two elements whose sum is closest to zero
• Find a pair with the given difference
• Kth smallest element in a row-wise and column-wise sorted 2D array
• Find common elements in three sorted arrays
• Ceiling in a sorted array
• Floor in a Sorted Array
• Find the maximum element in an array which is first increasing and then decreasing
• Given Array of size n and a number k, find all elements that appear more than n/k times

Medium problems on Searching algorithms

• Find all triplets with zero sum
• Find the element before which all the elements are smaller than it, and after which all are greater
• Find the largest pair sum in an unsorted array
• K’th Smallest/Largest Element in Unsorted Array
• Search an element in a sorted and rotated Array
• Find the Minimum element in a Sorted and Rotated Array
• Find a Fixed Point (Value equal to index) in a given array
• Find the k most frequent words from a file
• Find k closest elements to a given value
• Given a sorted array and a number x, find the pair in array whose sum is closest to x
• Find the closest pair from two sorted arrays
• Find three closest elements from given three sorted arrays
• Binary Search for Rational Numbers without using floating point arithmetic

Hard problems on Searching algorithms

• Median of two sorted arrays of same size
• Search in an almost sorted array
• Find position of an element in a sorted array of infinite numbers
• Find if there is a pair with a given sum in the rotated sorted Array
• K’th Smallest/Largest Element in Unsorted Array | Worst case Linear Time
• K'th largest element in a stream
• Best First Search (Informed Search)

Searching algorithms are essential tools in computer science used to locate specific items within a collection of data. These algorithms are designed to efficiently navigate through data structures to find the desired information, making them fundamental in various applications such as databases, web search engines , and more.

Searching Algorithm

Table of Content

What is Searching?

• Searching terminologies
• Importance of Searching in DSA
• Applications of Searching
• Basics of Searching Algorithms
• Comparisons Between Different Searching Algorithms
• Library Implementations of Searching Algorithms
• Easy Problems on Searching
• Medium Problems on Searching
• Hard Problems on Searching

Searching is the fundamental process of locating a specific element or item within a collection of data . This collection of data can take various forms, such as arrays, lists, trees, or other structured representations. The primary objective of searching is to determine whether the desired element exists within the data, and if so, to identify its precise location or retrieve it. It plays an important role in various computational tasks and real-world applications, including information retrieval, data analysis, decision-making processes, and more.

Searching terminologies:

Target element:.

In searching, there is always a specific target element or item that you want to find within the data collection. This target could be a value, a record, a key, or any other data entity of interest.

Search Space:

The search space refers to the entire collection of data within which you are looking for the target element. Depending on the data structure used, the search space may vary in size and organization.

Complexity:

Searching can have different levels of complexity depending on the data structure and the algorithm used. The complexity is often measured in terms of time and space requirements.

Deterministic vs. Non-deterministic:

Some searching algorithms, like  binary search , are deterministic, meaning they follow a clear, systematic approach. Others, such as linear search, are non-deterministic, as they may need to examine the entire search space in the worst case.

Importance of Searching in DSA:

• Efficiency:  Efficient searching algorithms improve program performance.
• Data Retrieval:  Quickly find and retrieve specific data from large datasets.
• Database Systems:  Enables fast querying of databases.
• Problem Solving:  Used in a wide range of problem-solving tasks.

Applications of Searching:

Searching algorithms have numerous applications across various fields. Here are some common applications:

• Information Retrieval: Search engines like Google, Bing, and Yahoo use sophisticated searching algorithms to retrieve relevant information from vast amounts of data on the web.
• Database Systems: Searching is fundamental in database systems for retrieving specific data records based on user queries, improving efficiency in data retrieval.
• E-commerce: Searching is crucial in e-commerce platforms for users to find products quickly based on their preferences, specifications, or keywords.
• Networking: In networking, searching algorithms are used for routing packets efficiently through networks, finding optimal paths, and managing network resources.
• Artificial Intelligence: Searching algorithms play a vital role in AI applications, such as problem-solving, game playing (e.g., chess), and decision-making processes
• Pattern Recognition: Searching algorithms are used in pattern matching tasks, such as image recognition, speech recognition, and handwriting recognition.

Basics of Searching Algorithms:

• Introduction to Searching – Data Structure and Algorithm Tutorial
• Importance of searching in Data Structure
• What is the purpose of the search algorithm?

Searching Algorithms:

• The Ubiquitous Binary Search

Comparisons Between Different Searching Algorithms:

Library implementations of searching algorithms:, easy problems on searching:.

• Find the largest three elements in an array
• Search, insert and delete in a sorted array
• Count 1’s in a sorted binary array
• Two elements whose sum is closest to zero
• k largest(or smallest) elements in an array
• Given an array of of size n and a number k, find all elements that appear more than n/k times

Medium Problems on Searching:

• Search an element in a sorted and rotated array
• Find the minimum element in a sorted and rotated array
• Find a peak element
• Maximum and minimum of an array using minimum number of comparisons
• Find a Fixed Point in a given array

Hard Problems on Searching:

• Median of two sorted arrays
• Median of two sorted arrays of different sizes
• Given a sorted and rotated array, find if there is a pair with a given sum
• K’th largest element in a stream

Quick Links:

• ‘Practice Problems’ on Searching
• ‘Quizzes’ on Searching

Recommended:

• Learn Data Structure and Algorithms | DSA Tutorial

Please Login to comment...

Similar reads, improve your coding skills with practice.

What kind of Experience do you want to share?