C++ Tutorial/STL Algorithms Modifying sequence operations/iter swap

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Swap first and second value with iter_swap

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
  1. include <iostream>
  2. include <list>
  3. include <algorithm>

using namespace std; /* PRINT_ELEMENTS()

* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/

template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {

   typename T::const_iterator pos;
   std::cout << optcstr;
   for (pos=coll.begin(); pos!=coll.end(); ++pos) {
       std::cout << *pos << " ";
   }
   std::cout << std::endl;

} int main() {

   list<int> coll;
   // insert elements from 1 to 9
   for (int i=1; i<=9; ++i) {
       coll.push_back(i);
   }
   PRINT_ELEMENTS(coll);
   // swap first and second value
   iter_swap (coll.begin(), ++coll.begin());
   PRINT_ELEMENTS(coll);
   // swap first and last value
   iter_swap (coll.begin(), --coll.end());
   PRINT_ELEMENTS(coll);

}</source>

1 2 3 4 5 6 7 8 9
2 1 3 4 5 6 7 8 9
9 1 3 4 5 6 7 8 2

Use iterators to swap elements at locations 0 and 1 of an array

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

  1. include <algorithm>
  2. include <iterator>

int main() {

  int a[ 10 ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
  std::ostream_iterator< int > output( cout, " " );
  cout << "Array a contains:\n   ";
  std::copy( a, a + 10, output );
  std::iter_swap( &a[ 0 ], &a[ 1 ] ); // swap with iterators
  cout << "\nArray a after swapping a[0] and a[1] using iter_swap:\n   ";
  std::copy( a, a + 10, output );
  cout << endl;
  return 0;

}</source>

Array a contains:
   1 2 3 4 5 6 7 8 9 10
Array a after swapping a[0] and a[1] using iter_swap:
   2 1 3 4 5 6 7 8 9 10