C++ <list> - swap() Function

The C++ <list> swap() function is used to exchange all elements of one list with all elements of another list. To apply this function, the data-type of both lists must be same, although the size may differ.

Syntax

C++98
C++11

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

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

Parameters

`lhs`	First list.
`rhs`	Second list.

Return Value

None.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the swap() function is used to exchange all elements of list MyList1 with all elements of list MyList2.

#include <iostream>
#include <list>
using namespace std;
 
int main (){
  list<int> MyList1{10, 20, 30, 40, 50};
  list<int> MyList2{5, 55, 555};

  list<int>::iterator it;

  cout<<"Before Swapping, The MyList1 contains:";
  for(it = MyList1.begin(); it != MyList1.end(); ++it)
    cout<<" "<<*it;
  cout<<"\nBefore Swapping, The MyList2 contains:";
  for(it = MyList2.begin(); it != MyList2.end(); ++it)
    cout<<" "<<*it;

  swap(MyList1, MyList2);

  cout<<"\n\nAfter Swapping, The MyList1 contains:";
  for(it = MyList1.begin(); it != MyList1.end(); ++it)
    cout<<" "<<*it;
  cout<<"\nAfter Swapping, The MyList2 contains:";
  for(it = MyList2.begin(); it != MyList2.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

Before Swapping, The MyList1 contains: 10 20 30 40 50
Before Swapping, The MyList2 contains: 5 55 555

After Swapping, The MyList1 contains: 5 55 555
After Swapping, The MyList2 contains: 10 20 30 40 50

❮ C++ <list> Library