iter_swap

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Contents
  1. Definition
  2. Interface
  3. Description
  4. Return Value
  5. Complexity
  6. References
  7. See Also

Swap values of objects pointed by two iterators

Computing Stl Algorithms Modifying

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Definition

The iter_swap() algorithm is defined in the standard header <algorithm> and the implementation is in <algobase.h>.

Interface

#include <algorithm>
template < class ForwardIterator1, class ForwardIterator2 >
   void iter_swap(
      ForwardIterator1 left,
      ForwardIterator2 right
   );

Parameters:

ParameterDescription
leftOne of the forward iterators whose value is to be exchanged
rightThe second of the forward iterators whose value is to be exchanged

Description

Iter_swap exchange the values pointed to by the two iterators left and right.

Iter_swap is equivalent to swap(*left, *right).

Return Value

None.

Complexity

Iter_swap algorithm has a constant complexity. It performs one copy construction and two assignments.

References

Example 1
Problem

This program illustrates the use of the STL iter_swap() algorithm to swap integer values that are pointed to by two different iterators that may point into the same vector of integers, or into two different vectors of integers.

Workings
#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int a1[] = {1, 2, 3, 4, 5};
  vector<int> v1(a1, a1+5);
  cout <<"\nHere are the contents of v1:\n";
  for (vector<int>::size_type i=0; i<v1.size(); i++)
    cout <<v1.at(i)<<" ";
  
  int a2[] = {2, 4, 6, 8, 10};
  vector<int> v2(a2, a2+5);
  cout <<"\nHere are the contents of v2:\n";
  for (vector<int>::size_type i=0; i<v2.size(); i++)
    cout <<v2.at(i)<<" ";

  cout <<"\nFirst we swap the end values in v1.";
  iter_swap(v1.begin(), v1.end()-1);
  cout <<"\nHere are the contents of the revised v1:\n";
  for (vector<int>::size_type i=0; i<v1.size(); i++)
    cout <<v1.at(i)<<" ";

  cout <<"\nThen we swap the middle values in v1 and v2.";
  iter_swap(v1.begin()+2, v2.begin()+2);
  cout <<"\nHere are the contents of the revised v1:\n";
  for (vector<int>::size_type i=0; i<v1.size(); i++)
    cout <<v1.at(i)<<" ";

  cout <<"\nHere are the contents of the revised v2:\n";
  for (vector<int>::size_type i=0; i<v2.size(); i++)
    cout <<v2.at(i)<<" ";

  return 0;
}
Solution

Output:

Here are the contents of v1:
1 2 3 4 5

Here are the contents of v2:
2 4 6 8 10

First we swap the end values in v1.
Here are the contents of the revised v1:
5 2 3 4 1

Then we swap the middle values in v1 and v2.
Here are the contents of the revised v1:
5 2 6 4 1

Here are the contents of the revised v2:
2 4 3 8 10

References

See Also