is_heap is_heap Category: algorithms Component type: function Prototype Is_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) Description Is_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. Definition Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h. This function is an SGI extension; it is not part of the C++ standard. Requirements on types For the first version: RandomAccessIterator is a model of Random Access Iterator. RandomAccessIterator's value type is a model of LessThan Comparable. The ordering on objects of RandomAccessIterator's value type is a strict weak ordering, as defined in the LessThan Comparable requirements. For the second version: RandomAccessIterator is a model of Random Access Iterator. StrictWeakOrdering is a model of Strict Weak Ordering. RandomAccessIterator's value type is convertible to StrictWeakOrdering's argument type. Preconditions [first, last) is a valid range. Complexity Linear. Zero comparisons if [first, last) is an empty range, otherwise at most (last - first) - 1 comparisons. Example int 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 also make_heap, push_heap, pop_heap, sort_heap Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation