Microsoft KB Archive/156301

= INFO: STL Sample for the partition Function =

Article ID: 156301

Article Last Modified on 6/23/2005

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Professional Edition

 Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Learning Edition 

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This article was previously published under Q156301

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SUMMARY
The sample code below illustrates how to use the partition, begin, end, and bind2nd STL functions in Visual C++.

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Prototype
template<class BidirectionalIterator, class Predicate> inline BidirectionalIterator partition(BidirectionalIterator first,                                  BidirectionalIterator last,                                   Predicate predicate) NOTE: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

Description
The partition algorithm arranges elements in the range [first, last) such that the elements for which predicate returns true are before the elements for which predicate returns false. The algorithm returns an iterator positioned at the first element for which predicate returns false.

Sample Code
////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // partition.cpp : Illustrates how to use the partition function. // // Functions: // //  partition  - Partition a range using a predicate. // //  begin      - Returns an iterator that points to the first element //               in a sequence. // //  end        - Returns an iterator that points one past the end of //                a sequence. // //  bind2nd    - Returns true for elements for which the condition //               is true. // // Written by Kalindi Sanghrajka // of Microsoft Product Support Services, // Software Core Developer Support. // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

// disable warning C4786: symbol greater than 255 character, // okay to ignore
 * 1) pragma warning(disable: 4786)

using namespace std;
 * 1) include
 * 2) include
 * 3) include
 * 4) include

void main {   const int VECTOR_SIZE = 8 ;

// Define a template class vector of integers typedef vector<int, allocator > IntVector ;

//Define an iterator for template class vector of integer typedef IntVector::iterator IntVectorIt ;

IntVector Numbers(VECTOR_SIZE) ;  //vector containing numbers

IntVectorIt start, end, it ;

start = Numbers.begin ;  // location of first // element of Numbers

end = Numbers.end ;      // one past the location // last element of Numbers

//Initialize vector Numbers Numbers[0] = 6 ; Numbers[1] = 20 ;

Numbers[2] = 10 ; Numbers[3] = 15 ; Numbers[4] = 12 ; Numbers[5] = 7 ; Numbers[6] = 9 ; Numbers[7] = 10 ;

cout << "Before calling partition" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// partition the sequence such that all the elements // less than 11 appear before all the elements greater than 11 it = partition(start, end, bind2nd(less, 11)) ;

cout << "After calling partition" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

} Output:

Before calling partition

Numbers { 6 20 10 15 12 7 9 10 }

After calling partition

Numbers { 6 10 10 9 7 12 15 20 }

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