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is_heap
PrototypeIs_heap is an overloaded name; there are actually two is_heap functions.template <class RandomAccessIterator> bool is_heap(RandomAccessIterator first, RandomAccessIterator last); template <class RandomAccessIterator, class StrictWeakOrdering> inline bool is_heap(RandomAccessIterator first, RandomAccessIterator last, StrictWeakOrdering comp) DescriptionIs_heap returns true if the range [first, last) is a heap [1], and false otherwise. The two versions 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.DefinitionDefined in the standard header algorithm, and in the nonstandard backwardcompatibility header algo.h. This function is an SGI extension; it is not part of the C++ standard.Requirements on typesFor the first version:
Preconditions
ComplexityLinear. Zero comparisons if [first, last) is an empty range, otherwise at most (last  first)  1 comparisons.Exampleint A[] = {1, 2, 3, 4, 5, 6, 7}; const int N = sizeof(A) / sizeof(int); assert(!is_heap(A, A+N)); make_heap(A, A+N); assert(is_heap(A, A+N)); Notes[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. See alsomake_heap, push_heap, pop_heap, sort_heapCopyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation
