Reverse contents of an array in C++

This post will discuss how to reverse the contents of an array in C++.

1. Using `std::reverse`

A simple solution to in-place reverse contents of an array is using the std::reverse algorithm from the standard library. The reverse algorithm is defined in the <algorithm> header and can be used as follows:

#include <iostream>

#include <algorithm>

#include <iterator>

int main()

{

int arr[] = {1, 2, 3, 4, 5};

std::reverse(std::begin(arr), std::end(arr));

for (int &i: arr) {

std::cout << i << ' ';

}

return 0;

}

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Output:

5 4 3 2 1

2. Using `std::swap`

Another alternative is to use the std::swap algorithm defined in the <algorithm> header. It works by swapping the values of objects pointed to by specified iterators. A typical invocation for the std::swap algorithm would look like below, to reverse an array:

#include <iostream>

#include <algorithm>

int main()

{

int arr[] = {1, 2, 3, 4, 5};

int n = sizeof(arr) / sizeof(*arr);

for (int i = 0; i < n / 2; i++) {

std::swap(arr[i], arr[n - i - 1]);

}

for (int &i: arr) {

std::cout << i << ' ';

}

return 0;

}

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Output:

5 4 3 2 1

We can even write a custom routine for the swapping task. It can be implemented as follows to reverse an array:

#include <iostream>

int main()

{

int arr[] = {1, 2, 3, 4, 5};

int n = sizeof(arr) / sizeof(*arr);

for (int i = 0; i < n / 2; i++) {

int temp = arr[n - i - 1];

arr[n - i - 1] = arr[i];

arr[i] = temp;

}

for (int &i: arr) {

std::cout << i << ' ';

}

return 0;

}

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Output:

5 4 3 2 1

That’s all about reversing the contents of an array in C++.

Reverse contents of an array in C++

1. Using std::reverse

2. Using std::swap

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1. Using `std::reverse`

2. Using `std::swap`