[alg.nth.element] (original) (raw)

template<class RandomAccessIterator> constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last);template<class ExecutionPolicy, class RandomAccessIterator> void nth_element(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last);template<class RandomAccessIterator, class Compare> constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp);template<class ExecutionPolicy, class RandomAccessIterator, class Compare> void nth_element(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp);template<random_­access_­iterator I, sentinel_­for<I> S, class Comp = ranges::less,class Proj = identity> requires sortable<I, Comp, Proj> constexpr I ranges::nth_element(I first, I nth, S last, Comp comp = {}, Proj proj = {});

Effects:After nth_­element the element in the position pointed to by nthis the element that would be in that position if the whole range were sorted with respect to comp and proj, unless nth == last.

Also for every iterator i in the range [first, nth)and every iterator j in the range [nth, last)it holds that:bool(invoke(comp, invoke(proj, *j), invoke(proj, *i))) is false.

template<random_­access_­range R, class Comp = ranges::less, class Proj = identity> requires sortable<iterator_t<R>, Comp, Proj> constexpr borrowed_iterator_t<R> ranges::nth_element(R&& r, iterator_t<R> nth, Comp comp = {}, Proj proj = {});