Forward List Swap in C++ STL

Given is the task to show the working of forward_list::swap( ) function in C++.

What is a Forward List?

Forward list is a sequence container that allow constant time insert and erase operations anywhere within the sequence. Forward list are implement as a singly-linked lists. The ordering is kept by the association to each element of a link to the next element in the sequence.

What is forward_list::swap()?

forward_list::swap( ) is a function in c++ standard library function which is used to swap the contents of one list to another list of same size and same data type.

Syntax

forward_list1.swap(forward_list2)

Or

swap(forward_list first, forward_list second)

Example

Output – First list : 57 99 54 34 84
   Second list : 45 65 78 96 77
   After swapping operation outputs are
   First list : 45 65 78 96 77
   Second list : 57 99 54 34 84

Output – First list : 44 37 68 94 73
   Second list : 20 11 87 29 40
   After swapping operation outputs are
   First list : 20 11 87 29 40
   Second list : 44 37 68 94 73

Approach can be followed

• First initialize the two forward list.

• Then we print the two forward list.

• Then we defines the swap( ) function.

• Then we print the forward list after swaping.

By using above approach we can swap the two forward list.

Algorithm

Start −

STEP 1 – Intialize the two forward list and print them
   First list forward_list<int> List1 = { 10, 20, 30, 40, 50 }
   for( auto x = list1.start( ); x != list1.end( ); ++x )
   cout<< *x << “ “ ;
   second list forward_list<in> list2 = { 40, 30, 20, 10, 50 }
   for( auto x = list2.start( ); x != list2.end( ); ++x )
   cout<< *x << “ “ ;
END

STEP 2 – create the swap function to perform swap operation.
   swap( list1, list2)
END

Stop

Example

// C++ code to demonstrate the working of forward_list::reverse( )
#include<iostream.h>
#include<forward_list.h>
Using namespace std;
Int main( ){
   // initializing two forward lists
   forward_list<int> list1 = { 10, 20, 30, 40, 50 }
      cout<< “ Elements of List1:”;
      for( auto x = list1.start( ); x != list1.end( ); ++x )
      cout<< *x << “ “ ;
   forward_list<int> list2 = { 40, 30, 20, 10, 50 }
      cout<< “Elements of List2:”;
      for( auto x = list2.start( ); x != list2.end( ); ++x )
      cout<< *x << “ “ ;
   // defining of function that performs the swap operation
   swap(list1, list2);
   cout<< “ After swapping List1 is :”;
   for(auto x = list1.start( ); x != list1.end( ); ++x)
      cout<< *x<< “ “;
   cout<< “ After swapping List2 is :”;
   for(auto x = list1.start( ); x!= list2.end( ); ++x)
      cout<< *x<< “ “;
   return 0;
}

Output

If we run the above code then it will generate the following output

OUTPUT – Elements of List1 : 10 20 30 40 50
   Elements of list2 : 40 30 20 10 50
   After Swapping List1 : 40 30 20 10 50
   After Swapping List2 : 10 20 30 40 50

OUTPUT – Elements of List1 : 23 56 78 49 11
   Elements of List2 : 11 49 78 56 23
   After Swapping List1 : 11 49 78 56 23
   After Swapping List1 : 23 56 78 49 11