Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.

NAME

  merge  - Merge two sorted sequences into a third sequence.

SYNOPSIS

  #include <algorithm>

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

  template <class InputIterator1, class InputIterator2,
           class OutputIterator, class Compare>
   OutputIterator
    merge(InputIterator1 first1, InputIterator1 last1,
         InputIterator2 first2, InputIterator last2,
         OutputIterator result, Compare comp);

DESCRIPTION

  The merge algorithm merges two sorted sequences, specified by [first1,
  last1) and [first2, last2), into the sequence specified by [result, result
  + (last1 - first1) + (last2 - first2)).  The first version of the merge
  algorithm uses the less than operator (<) to compare elements in the two
  sequences.  The second version uses the comparison function provided by the
  function call.  If a comparison function is provided, merge assumes that
  both sequences were sorted using that comparison function.

  The merge is stable. This means that if the two original sequences contain
  equivalent elements, the elements from the first sequence will always
  precede the matching elements from the second in the resulting sequence.
  The size of the result of a merge is equal to the sum of the sizes of the
  two argument sequences.  merge returns an iterator that points to the end
  of the resulting sequence, i.e., result + (last1 - first1) + (last2
  -first2). The result of merge is undefined if the resulting range overlaps
  with either of the original ranges.

  merge assumes that there are at least (last1 - first1) + (last2 - first2)
  elements following result, unless result has been adapted by an insert
  iterator.

COMPLEXITY

  For merge at most (last - first1) + (last2 - first2) - 1 comparisons are
  performed.

EXAMPLE

  //
  // merge.cpp
  //
   #include <algorithm>
   #include <vector>
   #include <iostream.h>

  int main()
   {
    int d1[4] = {1,2,3,4};
    int d2[8] = {11,13,15,17,12,14,16,18};

     // Set up two vectors
    vector<int> v1(d1,d1 + 4), v2(d1,d1 + 4);
     // Set up four destination vectors
    vector<int> v3(d2,d2 + 8),v4(d2,d2 + 8),
                v5(d2,d2 + 8),v6(d2,d2 + 8);
     // Set up one empty vector
    vector<int> v7;

     // Merge v1 with v2
     merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v3.begin());
     // Now use comparator
     merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v4.begin(),
          less<int>());

     // In place merge v5
    vector<int>::iterator mid = v5.begin();
    advance(mid,4);
    inplace_merge(v5.begin(),mid,v5.end());
     // Now use a comparator on v6
    mid = v6.begin();
    advance(mid,4);
    inplace_merge(v6.begin(),mid,v6.end(),less<int>());

     // Merge v1 and v2 to empty vector using insert iterator
     merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
          back_inserter(v7));

     // Copy all cout
    ostream_iterator<int,char> out(cout," ");
    copy(v1.begin(),v1.end(),out);
    cout << endl;
    copy(v2.begin(),v2.end(),out);
    cout << endl;
    copy(v3.begin(),v3.end(),out);
    cout << endl;
    copy(v4.begin(),v4.end(),out);
    cout << endl;
    copy(v5.begin(),v5.end(),out);
    cout << endl;
    copy(v6.begin(),v6.end(),out);
    cout << endl;
    copy(v7.begin(),v7.end(),out);
    cout << endl;

     // Merge v1 and v2 to cout
     merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
          ostream_iterator<int,char>(cout," "));
    cout << endl;

    return 0;
   }

  Output :
  1 2 3 4
  1 2 3 4
  1 1 2 2 3 3 4 4
  1 1 2 2 3 3 4 4
  11 12 13 14 15 16 17 18
  11 12 13 14 15 16 17 18
  1 1 2 2 3 3 4 4
  1 1 2 2 3 3 4 4

WARNING

  If your compiler does not support default template parameters then you need
  to always supply the Allocator template argument.  For instance you'll have
  to write:

  vector<int,allocator<int> >

  instead of:

  vector<int>

SEE ALSO

  Containers, inplace_merge

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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