Category: algorithms Component type: function


Make_heap is an overloaded name; there are actually two make_heap functions.
template <class RandomAccessIterator>
void make_heap(RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class StrictWeakOrdering>
void make_heap(RandomAccessIterator first, RandomAccessIterator last,
               StrictWeakOrdering comp);


Make_heap turns the range [first, last) into a heap [1].

The two versions of make_heap differ in how they define whether one element is less than another. The first version compares objects using operator<, and the second compares objects using a function object comp. In the first version the postcondition is that is_heap(first, last) is true, and in the second version the postcondition is that is_heap(first, last, comp) is true.


Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

Requirements on types

For the first version: For the second version:



Linear. At most 3*(last - first) comparisons.


int main()
  int A[] = {1, 4, 2, 8, 5, 7};
  const int N = sizeof(A) / sizeof(int);

  make_heap(A, A+N);
  copy(A, A+N, ostream_iterator<int>(cout, " "));
  cout << endl;

  sort_heap(A, A+N);
  copy(A, A+N, ostream_iterator<int>(cout, " "));
  cout << endl;


[1] A heap is a particular way of ordering the elements in a range of Random Access Iterators [f, l). The reason heaps are useful (especially for sorting, or as priority queues) is that they satisfy two important properties. First, *f is the largest element in the heap. Second, it is possible to add an element to a heap (using push_heap), or to remove *f, in logarithmic time. Internally, a heap is simply a tree represented as a sequential range. The tree is constructed so that that each node is less than or equal to its parent node.

See also

push_heap, pop_heap, sort_heap, sort, is_heap
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