C++ Vector Library - swap() Function

Description

The C++ function std::vector::swap() exchanges the contents of two vector.

Declaration

Following is the declaration for std::vector::swap() function form std::vector header.

template <class T, class Alloc>
void swap (vector<T,Alloc>& v1, vector<T,Alloc>& v2);

Parameters

• v1 − First vector container.

• v2 − Second vector container.

Return value

None.

Exceptions

This function never throws exception.

Time complexity

Linear i.e. O(1)

Example

The following example shows the usage of std::vector::swap() function.

#include <iostream>
#include <vector>

using namespace std;

int main(void) {
   vector<int> v1 = {1, 2, 3, 4, 5};
   vector<int> v2 = {10, 20, 30};

   cout << "Contents of vector v1 before swap operation" << endl;
   for (int i = 0; i < v1.size(); ++i)
      cout << v1[i] << endl;

   cout << "Contents of vector v2 before swap operation" << endl;
   for (int i = 0; i < v2.size(); ++i)
      cout << v2[i] << endl;

   swap(v1, v2);
   cout << "Contents of vector v1 after swap operation" << endl;
   for (int i = 0; i < v1.size(); ++i)
      cout << v1[i] << endl;

   cout << "Contents of vector v2 after swap operation" << endl;
   for (int i = 0; i < v2.size(); ++i)
      cout << v2[i] << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Contents of vector v1 before swap operation
1
2
3
4
5
Contents of vector v2 befor swap operation
10
20
30
Contents of vector v1 after swap operation
10
20
30
Contents of vector v2 after swap operation
1
2
3
4
5