DOCUMENT:Q156993  27-MAR-2002  [visualc]
TITLE   :INFO: STL Sample for the Predicate Version of nth_element Functi
PRODUCT :Microsoft C Compiler
PROD/VER::4.2,5.0,6.0
OPER/SYS:
KEYWORDS:kbcode kbVC420 kbVC500 kbVC600 kbDSupport

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The information in this article applies to:

 - The Standard C++ Library, used with:
    - Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0 
    - Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0 
    - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
    - Microsoft Visual C++.NET (2002) 
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NOTE: Microsoft Visual C++ NET (2002) supported both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model. The information in this article applies to unmanaged Visual C++ code only.

SUMMARY
=======

The sample code below illustrates how to use the predicate version of the
nth_element STL function in Visual C++.

MORE INFORMATION
================

Required Header
---------------

      <algorithm>

Prototype
---------

      template<class RandomAccessIterator, class Compare> inline
      void nth_element(RandomAccessIterator first,

                   RandomAccessIterator nth,
                       RandomAccessIterator last,
                       Compare compare)

NOTE: The class/parameter names in the prototype do not match the original
version in the header file. They have been modified to improve readability.

Description
-----------

The nth_element algorithm partitions the sequence [first..last) on the value
referenced by nth. All the elements less than or equal to the value are placed
before value and all elements greater than value are placed after value in the
sequence.

The predicate version of nth_element uses the compare function for comparisons.

Sample Code
-----------

   ////////////////////////////////////////////////////////////////////// 
   // 
   // Compile options needed: /GX
   // 
   // nth_element.cpp : Illustrates how to use the predicate version
   //                   of the nth_element function.
   // 
   // Functions:
   // 
   //    nth_element : Partition the elements in a sequence by its nth
   //                  element.
   // 
   // 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

   #pragma warning(disable: 4786)

   #include <iostream>
   #include <algorithm>
   #include <functional>
   #include <vector>

   #if _MSC_VER > 1020   // if VC++ version is > 4.2
      using namespace std;  // std c++ libs implemented in std
      #endif

   void main()

   {

       const int VECTOR_SIZE = 8 ;

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

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

       IntVector Numbers(VECTOR_SIZE) ;

       IntVectorIt start, end, it ;

       // Initialize vector Numbers
       Numbers[0] = 4 ;
       Numbers[1] = 10;
       Numbers[2] = 70 ;
       Numbers[3] = 30 ;
       Numbers[4] = 10;
       Numbers[5] = 69 ;
       Numbers[6] = 96 ;
       Numbers[7] = 100;

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

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

       cout << "Before calling nth_element:\n" << endl ;

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

       // partition the elements by the 4th element
       nth_element(start, start+4, end, less<int>()) ;

       cout << "After calling nth_element:\n" << endl ;

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

   }

Program Output is:

Before calling nth_element:

Numbers { 4 10 70 30 10 69 96 100  }

After calling nth_element:

Numbers { 4 10 10 30 69 70 96 100  }

REFERENCES
==========

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.

Additional query words: STL STLSample nth_element kbSTL kbTemplate

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Keywords          : kbcode kbVC420 kbVC500 kbVC600 kbDSupport 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : :4.2,5.0,6.0
Issue type        : kbinfo

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