C++ Programming Code Examples

C++ > Visual C++ 5.0 Standard C++ Library Code Examples

The merge algorithm merges two sorted sequences: [first1..last1) and [first2..last2)



The merge algorithm merges two sorted sequences: [first1..last1) and [first2..last2)


merge
	
 
Header
<algorithm>

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

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.

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

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 the 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.


Samples
Sample for Non-Predicate Version

// 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

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  }

Sample for Predicate Version

// 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, 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

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  }