STL Sample for the Predicate Version of the merge Function

ID: Q157561

The information in this article applies to:

The Standard C++ Library, included with:
- Microsoft Visual C++ 32-bit Edition, version 4.2

SUMMARY

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

MORE INFORMATION

Required Header


   <algorithm>

Prototype


   template<class InputIterator1,
            class InputIterator2,
            class OutputIterator
            class Compare> inline
   OutputIterator merge( InputIterator1 first1,
                         InputIterator1 last1,
                         InputIterator2 first2,
                         InputIterator2 last2
                         OutputIterator result,
                         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 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 compare function. 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 predicate version of 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>

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, less<int>()) ;

    // 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(), less<int>()) ;

    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 : kbcode STLIss
Version : winnt:
Platform : winnt
Issue type : kbhowto