Category: algorithms | Component type: function |
template <class RandomAccessIterator> void push_heap(RandomAccessIterator first, RandomAccessIterator last); template <class RandomAccessIterator, class StrictWeakOrdering> void push_heap(RandomAccessIterator first, RandomAccessIterator last, StrictWeakOrdering comp);
The two versions of push_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. The postcondition for the first version is that is_heap(first, last) is true, and the postcondition for the second version is that is_heap(first, last, comp) is true.
int main() { int A[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; make_heap(A, A + 9); cout << "[A, A + 9) = "; copy(A, A + 9, ostream_iterator<int>(cout, " ")); push_heap(A, A + 10); cout << endl << "[A, A + 10) = "; copy(A, A + 10, ostream_iterator<int>(cout, " ")); cout << endl; }
The output is
[A, A + 9) = 8 7 6 3 4 5 2 1 0 [A, A + 10) = 9 8 6 3 7 5 2 1 0 4
[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 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.