Place all elements in the range [ first ... last ) that cause pred to evaluate to true before all elements in the range that cause pred to evaluate to false . Return an iterator positioned at the first element of the second sequence.

Declaration


  
#include <algorithm>

template< class BidirectionalIterator, class Predicate >
BidirectionalIterator partition
  (
  BidirectionalIterator first,
  BidirectionalIterator last,
  Predicate pred
  );

Complexity

Time complexity is O(N), where N = ( last - first ), as pred will be evaluated N times and at most N / 2 swaps will be performed.

Example <ospace/osstd/examples/ptition0.cpp>


    #include <iostream>
#include <algorithm>

int numbers[ 6 ] = { 6, 12, 3, 10, 1, 20 };

int
less_10( int a_ )
  {
  return a_ < 10 ? 1 : 0;
  }

void
main()
  {
  partition( numbers, numbers + 6, less_10 );

  for ( int i = 0; i < 6; ++i )
    cout << numbers[ i ] << ` `;
  cout << "\n";
  }

6 1 3 10 12 20

Example <ospace/osstd/examples/ptition1.cpp>


    #include <iostream>
#include <stdlib.h>
#include <algorithm>
#include <functional>
#include <iterator>
#include <vector>

void
main()
  {
  vector< int > v1( 10 );
  for ( int i = 0; i < v1.size(); ++i )
    v1[ i ] = rand() % 20;
  ostream_iterator< int > iter( cout, " " );
  copy( v1.begin(), v1.end(), iter );
  cout << "\n";

  partition( v1.begin(), v1.end(), bind2nd( less< int >(), 11 ) );

  copy( v1.begin(), v1.end(), iter );
  cout << "\n";
  }

6 10 2 10 16 17 15 15 8 6
6 10 2 10 6 8 15 15 17 16

partition

Library

Declaration

Complexity

Example <ospace/osstd/examples/ptition0.cpp>

Example <ospace/osstd/examples/ptition1.cpp>