Category: algorithms | Component type: function |
template <class RandomAccessIterator> void make_heap(RandomAccessIterator first, RandomAccessIterator last); template <class RandomAccessIterator, class StrictWeakOrdering> void make_heap(RandomAccessIterator first, RandomAccessIterator last, StrictWeakOrdering comp);
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.
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.