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

NAME

  sort_heap  - Converts a heap into a sorted collection.

SYNOPSIS

  #include <algorithm>

  template <class RandomAccessIterator>
   void
    sort_heap(RandomAccessIterator first,
             RandomAccessIterator last);

  template <class RandomAccessIterator, class Compare>
   void
    sort_heap(RandomAccessIterator first,
             RandomAccessIterator last, Compare comp);

DESCRIPTION

  A heap is a particular organization of elements in a range between two
  random access iterators [a, b).  Its two key properties are:

  1. *a is the largest element in the range.

  2. *a may be removed by pop_heap(), or a new element added by push_heap(),
       in O(logN) time.

  These properties make heaps useful as priority queues.

  The sort_heap algorithm converts a heap into a sorted collection over the
  range [first, last) using either the default operator (<) or the comparison
  function supplied with the algorithm.  Note that sort_heap is not stable,
  i.e., the elements may not be in the same relative order after sort_heap is
  applied.

COMPLEXITY

  sort_heap performs at most NlogN comparisons where N is equal to last -
  first.

EXAMPLE

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

  int main(void)
   {
    int d1[4] = {1,2,3,4};
    int d2[4] = {1,3,2,4};

     // Set up two vectors
    vector<int> v1(d1,d1 + 4), v2(d2,d2 + 4);

     // Make heaps
    make_heap(v1.begin(),v1.end());
    make_heap(v2.begin(),v2.end(),less<int>());
     // v1 = (4,x,y,z)  and  v2 = (4,x,y,z)
     // Note that x, y and z represent the remaining
     // values in the container (other than 4).
     // The definition of the heap and heap operations
     // does not require any particular ordering
     // of these values.

     // Copy both vectors to cout
    ostream_iterator<int,char> out(cout," ");
    copy(v1.begin(),v1.end(),out);
    cout << endl;
    copy(v2.begin(),v2.end(),out);
    cout << endl;

     // Now let's pop
    pop_heap(v1.begin(),v1.end());
    pop_heap(v2.begin(),v2.end(),less<int>());
     // v1 = (3,x,y,4) and v2 = (3,x,y,4)

     // Copy both vectors to cout
    copy(v1.begin(),v1.end(),out);
    cout << endl;
    copy(v2.begin(),v2.end(),out);
    cout << endl;

     // And push
    push_heap(v1.begin(),v1.end());
    push_heap(v2.begin(),v2.end(),less<int>());
     // v1 = (4,x,y,z) and v2 = (4,x,y,z)

     // Copy both vectors to cout
    copy(v1.begin(),v1.end(),out);
    cout << endl;
    copy(v2.begin(),v2.end(),out);
    cout << endl;

     // Now sort those heaps
     sort_heap(v1.begin(),v1.end());
     sort_heap(v2.begin(),v2.end(),less<int>());
     // v1 = v2 = (1,2,3,4)

     // Copy both vectors to cout
    copy(v1.begin(),v1.end(),out);
    cout << endl;
    copy(v2.begin(),v2.end(),out);
    cout << endl;

    return 0;
   }

  Output :
  4 2 3 1
  4 3 2 1
  3 2 1 4
  3 1 2 4
  4 3 1 2
  4 3 2 1
  1 2 3 4
  1 2 3 4

WARNING

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

  vector<int, allocator<int> >

  instead of :

  vector<int>

SEE ALSO

  make_heap, pop_heap, push_heap

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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