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Section: 27.8.9 [alg.min.max] Status: CD1 Submitter: Matt Austern Opened: 2007-08-30 Last modified: 2016-01-28
Priority: Not Prioritized
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The complexity for minmax_element (27.8.9 [alg.min.max] par 16) says "At most max(2 * (last - first ) - 2, 0) applications of the corresponding comparisons", i.e. the worst case complexity is no better than calling min_element and max_element separately. This is gratuitously inefficient. There is a well known technique that does better: see section 9.1 of CLRS (Introduction to Algorithms, by Cormen, Leiserson, Rivest, and Stein).
Change 27.8.9 [alg.min.max] to:
template<class ForwardIterator> pair<ForwardIterator, ForwardIterator> minmax_element(ForwardIterator first , ForwardIterator last); template<class ForwardIterator, class Compare> pair<ForwardIterator, ForwardIterator> minmax_element(ForwardIterator first , ForwardIterator last , Compare comp);
Returns: make_pair(m, M), where m is
min_element(first, last) or min_element(first, last, comp)and M is max_element(first, last) or max_element(first, last, comp).
Complexity: At most
max(2 * (last - first ) - 2, 0)applications of the corresponding comparisons.