push_heap

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Contents
  1. Definition
  2. Interface
  3. Description
  4. Return Value
  5. Complexity
  6. References
  7. See Also

Adds an element to a heap

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Computing Stl Algorithms Heap

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Definition

The push_heap() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.

Interface

#include <algorithm>
template < class RandomAccessIterator >
   void push_heap(
      RandomAccessIterator first, 
      RandomAccessIterator last
   );
template < class RandomAccessIterator, class BinaryPredicate >
   void push_heap(
      RandomAccessIterator first, 
      RandomAccessIterator last,
      BinaryPredicate comp
   );

Parameters:

ParameterDescription
firstA random-access iterator addressing the position of the first element in the heap
lastA random-access iterator addressing the position one past the final element in the range to be converted into a heap
compUser-defined predicate function object that defines sense in which one element is less than another. A binary predicate takes two arguments and returns true when satisfied and false when not satisfied

Description

Push_heap inserts the element at the position last - 1 into the heap defined by the range [first, last-1).

The first version compares objects using operator< and the second compares objects using a function object comp.

Return Value

None.

Complexity

The complexity is linear; performs at most log(last - first) comparisons.

References

Example 1
Problem

This program illustrates the use of the STL push_heap() algorithm (default version) to add a value to a (maximum) heap of integers.

Workings
#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int a[] = {36, 19, 25, 17, 3, 7, 1, 2,};
  vector<int> v(a, a+8);

  cout <<"\nHere are the values in the vector (the heap):\n";
  for (vector<int>::size_type i=0; i<v.size(); i++)
    cout <<v.at(i)<<" ";

  cout <<"\nNow we add the value 100 to the heap.";
  v.push_back(100);
  push_heap(v.begin(), v.end());

  cout <<"\nHere are the revised contents of the vector (the new heap):\n";
  for (vector<int>::size_type i=0; i<v.size(); i++)
    cout <<v.at(i)<<" ";

  return 0;
}
Solution

Output:

Here are the values in the vector (the heap):
36 19 25 17 3 7 1 2

Now we add the value 100 to the heap.

Here are the revised contents of the vector (the new heap):
100 36 25 19 3 7 1 2 17

References

See Also