unordered_set swap() in C++

swap(): This function is available in the File: unordered_set.h. This function is a build-in function in STL of C++. This function swaps data with another unordered_set.

Syntax:

void std::unordered_set<int>::swap(std::unordered_set<int> &__x)

This function takes one argument of type unordered_set as its parameter. This function swaps data with another unordered_set.

Parameters: One parameter is required for this method.

__x – An unordered_set of the same element and allocator types.

This exchanges the elements between two sets in constant time.

File: unordered_set.h

Approach

C++

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

int main()
{
    unordered_set<int> st1 = {9, 4, 5};

    unordered_set<int> st2 = {10, 25, 124, 67};

    cout << "unordered_set 1 size before swap :" << 
             st1.size() << "\n";
    cout << "unordered_set 2 size before swap :" << 
             st2.size() << "\n";

    st1.swap(st2);

    cout << "\n";

    cout << "unordered_set 1 size after swap :" << 
             st1.size() << "\n";
    cout << "unordered_set 2 size after swap :" << 
             st2.size() << "\n";
    return 0;
}

Output:

unordered_set 1 size before swap :3
unordered_set 2 size before swap :4

unordered_set 1 size after swap :4
unordered_set 2 size after swap :3