Swap operation on a vector in C++

This post will discuss swap operation on a vector in C++.

Here’s a three-line implementation of the swap function in C using pointers.

void swap(int *x, int *y)

{

int temp = *x;

*x = *y;

*y = temp;

}

Let’s discuss various methods to do this in C++:

1. Using `std::move` function

We can use std::move introduced by the C++11 to swap two objects, as shown below:

#include <iostream>

#include <vector>

template <typename T>

void swap(T &x, T &y)

{

T temp = std::move(x);

x = std::move(y);

y = std::move(temp);

}

// before C++11

template <typename T>

void swap(T &x, T &y)

{

T temp = x;

x = y;

y = temp;

}*/

int main()

{

std::vector<int> nums = { 0, 1, 2, 3, 4 };

int i = 2, j = 3;

swap(nums[i], nums[j]);

for (int i: nums) {

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

}

return 0;

}

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Output:

0 1 3 2 4

2. Using `std::swap` function

The standard solution is to use the std::swap algorithm defined in the <utility> header (in C++11). It works by swapping the values of two objects.

#include <iostream>

#include <vector>

#include <utility>

int main()

{

std::vector<int> nums = { 0, 1, 2, 3, 4 };

int i = 2, j = 3;

std::swap(nums[i], nums[j]);

for (int i: nums) {

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

}

return 0;

}

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Output:

0 1 3 2 4

3. Using `std::iter_swap` function

Another alternative is to use the std::iter_swap algorithm defined in the <algorithm> header. It works by swapping the values of objects pointed to by specified iterators.

#include <iostream>

#include <vector>

#include <iterator>

#include <algorithm>

int main()

{

std::vector<int> nums = { 0, 1, 2, 3, 4 };

int i = 2, j = 3;

auto itr_i = std::next(nums.begin(), i);

auto itr_j = std::next(nums.begin(), j);

std::iter_swap(itr_i, itr_j);

for (int i: nums) {

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

}

return 0;

}

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Output:

0 1 3 2 4

That’s all about swap operation on a vector in C++.

Swap operation on a vector in C++

1. Using std::move function

2. Using std::swap function

3. Using std::iter_swap function

Share this:

1. Using `std::move` function

2. Using `std::swap` function

3. Using `std::iter_swap` function