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partial_sort_copy
PrototypePartial_sort_copy is an overloaded name; there are actually two partial_sort_copy functions.template <class InputIterator, class RandomAccessIterator> RandomAccessIterator partial_sort_copy(InputIterator first, InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last); template <class InputIterator, class RandomAccessIterator, class StrictWeakOrdering> RandomAccessIterator partial_sort_copy(InputIterator first, InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp); DescriptionPartial_sort_copy copies the smallest N elements from the range [first, last) to the range [result_first, result_first + N), where N is the smaller of last  first and result_last  result_first. The elements in [result_first, result_first + N) will be in ascending order.The two versions of partial_sort_copy 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 of partial_sort_copy is as follows. If i and j are any two valid iterators in the range [result_first, result_first + N) such that i precedes j, then *j < *i will be false. The corresponding postcondition for the second version is that comp(*j, *i) will be false. The return value is result_first + N. DefinitionDefined in the standard header algorithm, and in the nonstandard backwardcompatibility header algo.h.Requirements on typesFor the first version:
Preconditions
ComplexityApproximately (last  first) * log(N) comparisons, where N is the smaller of last  first and result_last  result_first.Exampleint A[] = {7, 2, 6, 11, 9, 3, 12, 10, 8, 4, 1, 5}; const int N = sizeof(A) / sizeof(int); vector<int> V(4); partial_sort_copy(A, A + N, V.begin(), V.end()); copy(V.begin(), V.end(), ostream_iterator<int>(cout, " ")); // The printed result is "1 2 3 4". NotesSee alsopartial_sort, sort, stable_sort, binary_search, lower_bound, upper_bound, less<T>, StrictWeakOrdering, LessThan ComparableCopyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation
