swap() in C++

The function std::swap() is a built-in function in the C++ Standard Template Library (STL) which swaps the value of two variables.

Syntax:

swap(a, b)

Parameters:

The function accepts two mandatory parameters a and b which are to be swapped. The parameters can be of any data type.

Return Value:

The function does not return anything, it swaps the values of the two variables. Programs below illustrate the swap() function:

Time Complexity: O(1)

Space Complexity: O(1)

Program 1:

CPP

// C++ program for illustration of swap() function
#include <bits/stdc++.h>
using namespace std;

int main()
{
    int a = 10;
    int b = 20;
    cout << "Value of a before: " << a << endl;
    cout << "Value of b before: " << b << endl;

    // swap values of the variables
    swap(a, b);
    cout << "Value of a now: " << a << endl;
    cout << "Value of b now: " << b << endl;
    return 0;
}

Output

Value of a before: 10
Value of b before: 20
Value of a now: 20
Value of b now: 10

Program 2:

CPP

#include <bits/stdc++.h>
using namespace std;

int main()
{
    string a = "Geeks";
    string b = "function";
    cout << "Value of a before: " << a << endl;
    cout << "Value of b before: " << b << endl;
    swap(a, b);
    cout << "Value of a now: " << a << endl;
    cout << "Value of b now: " << b << endl;
    return 0;
}

Output

Value of a before: Geeks
Value of b before: function
Value of a now: function
Value of b now: Geeks