merge (STL Sample)

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

Required Header:
<algorithm>

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 version in the header file. Some 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.
//////////////////////////////////////////////////////////////////////

// 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> 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> 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> 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  }