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Q157560: STL Sample for the merge Function

Article: Q157560
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): _IK
Last Modified: 05-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Standard C++ Library, included with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 4.2 
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SUMMARY
=======

The sample code below illustrates how to use the merge STL function in Visual
C++.

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

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

     <algorithm>

Prototype
---------

     template<class InputIterator1,
              class InputIterator2,
              class OutputIterator> inline
     OutputIterator merge( InputIterator1 first1,
                           InputIterator1 last1,
                           InputIterator2 first2,
                           InputIterator2 last2
                           OutputIterator result )

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 merge algorithm merges two sorted sequences: [first1..last1) and
[first2..last2) into a single sorted sequence starting at result.

This version assumes that the ranges [first1..last1) and [first2..last2) are
sorted using operator<. If both ranges contain equal values, the value from
the first range will be stored first.

The result of merging overlapping ranges is undefined.

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

  ////////////////////////////////////////////////////////////////////// 
  // 
  // Compile options needed: /GX
  // 
  // merge.cpp : Illustrates how to use the merge
  //                     function.
  // 
  // Functions:
  // 
  //    merge : Merge two sorted sequences
  //            into a single sorted list.
  // 
  // 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 <vector>
  #include <list>
  #include <deque>
  using namespace std;

  void main()
  {
      const int MAX_ELEMENTS = 8 ;

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

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

      IntVector NumbersVector(MAX_ELEMENTS) ;

      IntVectorIt startv, endv, itv ;

      // Define a template class list of int
      typedef list<int, allocator<int> > IntList ;

      //Define an iterator for template class list of ints
      typedef IntList::iterator IntListIt ;

      IntList NumbersList ;

      IntListIt first, last, itl ;

      // Define a template class deque of int
      typedef deque<int, allocator<int> > IntDeque ;

      //Define an iterator for template class deque of ints
      typedef IntDeque::iterator IntDequeIt ;

      IntDeque NumbersDeque(2 * MAX_ELEMENTS) ;

      IntDequeIt itd ;

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

      startv = NumbersVector.begin() ;   // location of first
                                         // element of NumbersVector

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

      // sort NumbersVector, merge requires the sequences
      // to be sorted
      sort(startv, endv) ;

      // print content of NumbersVector
      cout << "NumbersVector { " ;
      for(itv = startv; itv != endv; itv++)
          cout << *itv << " " ;
      cout << " }\n" << endl ;

      // Initialize vector NumbersList
      for(int i = 0; i < MAX_ELEMENTS; i++)
          NumbersList.push_back(i) ;

      first = NumbersList.begin() ;   // location of first
                                       // element of NumbersList

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

      // print content of NumbersList
      cout << "NumbersList { " ;
      for(itl = first; itl != last; itl++)
          cout << *itl << " " ;
      cout << " }\n" << endl ;

      // merge the elements of NumbersVector
      // and NumbersList and place the
      // results in NumbersDeque
      merge(startv, endv, first, last, NumbersDeque.begin()) ;

      cout << "After calling merge\n" << endl ;

      // print content of NumbersDeque
      cout << "NumbersDeque { " ;
      for(itd = NumbersDeque.begin();
          itd != NumbersDeque.end(); itd++)
          cout << *itd << " " ;
      cout << " }\n" << endl ;
  }

  Program Output is:

  NumbersVector { 4 10 10 30 69 70 96 100  }

  NumbersList { 0 1 2 3 4 5 6 7  }

  After calling merge

  NumbersDeque { 0 1 2 3 4 4 5 6 7 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 merge

======================================================================
Keywords          : _IK 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : winnt:
Issue type        : kbhowto

=============================================================================

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