C++ <forward_list> - swap() Function

The C++ forward_list::swap function is used to exchange all elements of one forward_list with all elements of another forward_list. To apply this function, the data-type of both forward_lists must be same, although the size may differ.

Syntax

C++11

template<class T, class Alloc>
void swap(
    forward_list<T,Alloc>& lhs,
    forward_list<T,Alloc>& rhs 
);

Parameters

`lhs`	First forward_list.
`rhs`	Second forward_list.

Return Value

None.

Time Complexity

Constant i.e, Θ(1).

Example:

In the below example, the forward_list::swap function is used to exchange all elements of forward_list f_list1 with all elements of forward_list f_list2.

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  forward_list<int> f_list1{10, 20, 30, 40, 50};
  forward_list<int> f_list2{5, 55, 555};

  forward_list<int>::iterator it;

  cout<<"Before Swapping, The f_list1 contains:";
  for(it = f_list1.begin(); it != f_list1.end(); ++it)
    cout<<" "<<*it;
  cout<<"\nBefore Swapping, The f_list2 contains:";
  for(it = f_list2.begin(); it != f_list2.end(); ++it)
    cout<<" "<<*it;

  swap(f_list1, f_list2);

  cout<<"\n\nAfter Swapping, The f_list1 contains:";
  for(it = f_list1.begin(); it != f_list1.end(); ++it)
    cout<<" "<<*it;
  cout<<"\nAfter Swapping, The f_list2 contains:";
  for(it = f_list2.begin(); it != f_list2.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

Before Swapping, The f_list1 contains: 10 20 30 40 50
Before Swapping, The f_list2 contains: 5 55 555

After Swapping, The f_list1 contains: 5 55 555
After Swapping, The f_list2 contains: 10 20 30 40 50

❮ C++ <forward_list> Library