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iter_swap 

Exchanges two values referred to by a pair of specified iterators.


template<class ForwardIterator1, class ForwardIterator2>
   void iter_swap(
      ForwardIterator1 _Left,
      ForwardIterator2 _Right
   );

Parameters

_Left

One of the forward iterators whose value is to be exchanged.

_Right

The second of the forward iterators whose value is to be exchanged.

swap should be used in preference to iter_swap, which was included in the C++ Standard for backward compatibility. If Fit1 and Fit2 are forward iterators, then iter_swap ( Fit1, Fit2 ), is equivalent to swap ( *Fit1, *Fit2 ).

The value types of the input forward iterators must have the same value.

// alg_iter_swap.cpp
// compile with: /EHsc
#include <vector>
#include <deque>
#include <algorithm>
#include <iostream>
#include <ostream>

using namespace std;
class CInt;
ostream& operator<<( ostream& osIn, const CInt& rhs );

class CInt
{
public:
   CInt( int n = 0 ) : m_nVal( n ){}
   CInt( const CInt& rhs ) : m_nVal( rhs.m_nVal ){}
   CInt&   operator=( const CInt& rhs ) { m_nVal =
   rhs.m_nVal; return *this; }
   bool operator<( const CInt& rhs ) const
      { return ( m_nVal < rhs.m_nVal );}
   friend ostream& operator<<( ostream& osIn, const CInt& rhs );

private:
   int m_nVal;
};

inline ostream& operator<<( ostream& osIn, const CInt& rhs )
{
   osIn << "CInt(" << rhs.m_nVal << ")";
   return osIn;
}

// Return whether modulus of elem1 is less than modulus of elem2
bool mod_lesser ( int elem1, int elem2 )
{
   if ( elem1 < 0 )
      elem1 = - elem1;
   if ( elem2 < 0 )
      elem2 = - elem2;
   return elem1 < elem2;
};

int main( )
{
   CInt c1 = 5, c2 = 1, c3 = 10;
   deque<CInt> deq1;
   deque<CInt>::iterator d1_Iter;

   deq1.push_back ( c1 );
   deq1.push_back ( c2 );
   deq1.push_back ( c3 );

   cout << "The original deque of CInts is deq1 = (";
   for ( d1_Iter = deq1.begin( ); d1_Iter != --deq1.end( ); d1_Iter++ )
      cout << " " << *d1_Iter << ",";
   d1_Iter = --deq1.end( );
   cout << " " << *d1_Iter << " )." << endl;

   // Exchanging first and last elements with iter_swap
   iter_swap ( deq1.begin ( ) , --deq1.end ( ) );

   cout << "The deque of CInts with first & last elements swapped is:\n deq1 = (";
   for ( d1_Iter = deq1.begin( ); d1_Iter != --deq1.end( ); d1_Iter++ )
      cout << " " << *d1_Iter << ",";
   d1_Iter = --deq1.end( );
   cout << " " << *d1_Iter << " )." << endl;

   // Swapping back first and last elements with swap
   swap ( *deq1.begin ( ) , *(deq1.end ( ) -1 ) );

   cout << "The deque of CInts with first & last elements swapped back is:\n deq1 = (";
   for ( d1_Iter = deq1.begin( ); d1_Iter != --deq1.end( ); d1_Iter++ )
      cout << " " << *d1_Iter << ",";
   d1_Iter = --deq1.end( );
   cout << " " << *d1_Iter << " )." << endl;

   // Swapping a vector element with a deque element
   vector <int> v1;
   vector <int>::iterator Iter1;
   deque <int> deq2;
   deque <int>::iterator d2_Iter;

   int i;
   for ( i = 0 ; i <= 3 ; i++ )
   {
      v1.push_back( i );
   }

   int ii;
   for ( ii = 4 ; ii <= 5 ; ii++ )
   {
      deq2.push_back( ii );
   }

   cout << "Vector v1 is ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")." << endl;

   cout << "Deque deq2 is ( " ;
   for ( d2_Iter = deq2.begin( ) ; d2_Iter != deq2.end( ) ; d2_Iter++ )
      cout << *d2_Iter << " ";
   cout << ")." << endl;

   iter_swap ( v1.begin ( ) , deq2.begin ( ) );

   cout << "After exchanging first elements,\n vector v1 is: v1 = ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")." << endl << " & deque deq2 is: deq2 = ( ";
   for ( d2_Iter = deq2.begin( ) ; d2_Iter != deq2.end( ) ; d2_Iter++ )
      cout << *d2_Iter << " ";
   cout << ")." << endl;
}

Output

The original deque of CInts is deq1 = ( CInt(5), CInt(1), CInt(10) ).
The deque of CInts with first & last elements swapped is:
 deq1 = ( CInt(10), CInt(1), CInt(5) ).
The deque of CInts with first & last elements swapped back is:
 deq1 = ( CInt(5), CInt(1), CInt(10) ).
Vector v1 is ( 0 1 2 3 ).
Deque deq2 is ( 4 5 ).
After exchanging first elements,
 vector v1 is: v1 = ( 4 1 2 3 ).
 & deque deq2 is: deq2 = ( 0 5 ).

Header: <algorithm>

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