std::ranges::partial_sort_copy, std::ranges::partial_sort_copy_result
| 定義於標頭檔案 <algorithm> |
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| 呼叫簽名 (Call signature) |
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| template< std::input_iterator I1, std::sentinel_for<I1> S1, std::random_access_iterator I2, std::sentinel_for<I2> S2, |
(1) | (C++20 起) |
| template< ranges::input_range R1, ranges::random_access_range R2, class Comp = ranges::less, class Proj1 = std::identity, |
(2) | (C++20 起) |
| 輔助型別 |
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| template< class I, class O > using partial_sort_copy_result = ranges::in_out_result<I, O>; |
(3) | (C++20 起) |
將源範圍 [first, last) 的前 N 個元素複製到目標範圍 [result_first, result_first + N)，如同它們已根據 comp 和 proj1 進行了部分排序。其中 N = min(L₁, L₂)，L₁ 等於 ranges::distance(first, last)，L₂ 等於 ranges::distance(result_first, result_last)。
不保證相等元素的順序得到保留。
本頁描述的類函式實體是 演算法函式物件（非正式地稱為 niebloids），即
目錄 |
[編輯] 引數
| first, last | - | 定義要複製的源元素範圍的迭代器-哨兵對 |
| r | - | 要複製的源範圍 |
| result_first, result_last | - | 定義目標元素範圍的迭代器-哨兵對 |
| result_r | - | 目標範圍 |
| comp | - | 應用於投影元素的比較 |
| proj1 | - | 應用於源範圍元素的投影 |
| proj2 | - | 應用於目標範圍元素的投影 |
[編輯] 返回值
一個等於 {last, result_first + N} 的物件。
[編輯] 複雜度
至多 L₁•log(N) 次比較和 2•L₁•log(N) 次投影。
[編輯] 可能的實現
struct partial_sort_copy_fn { template<std::input_iterator I1, std::sentinel_for<I1> S1, std::random_access_iterator I2, std::sentinel_for<I2> S2, class Comp = ranges::less, class Proj1 = std::identity, class Proj2 = std::identity> requires std::indirectly_copyable<I1, I2> && std::sortable<I2, Comp, Proj2> && std::indirect_strict_weak_order<Comp, std::projected<I1, Proj1>, std::projected<I2, Proj2>> constexpr ranges::partial_sort_copy_result<I1, I2> operator()(I1 first, S1 last, I2 result_first, S2 result_last, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const { if (result_first == result_last) return {std::move(ranges::next(std::move(first), std::move(last))), std::move(result_first)}; auto out_last{result_first}; // copy first N elements for (; !(first == last or out_last == result_last); ++out_last, ++first) *out_last = *first; // convert N copied elements into a max-heap ranges::make_heap(result_first, out_last, comp, proj2); // process the rest of the input range (if any), preserving the heap property for (; first != last; ++first) { if (std::invoke(comp, std::invoke(proj1, *first), std::invoke(proj2, *result_first))) { // pop out the biggest item and push in a newly found smaller one ranges::pop_heap(result_first, out_last, comp, proj2); *(out_last - 1) = *first; ranges::push_heap(result_first, out_last, comp, proj2); } } // first N elements in the output range is still // a heap - convert it into a sorted range ranges::sort_heap(result_first, out_last, comp, proj2); return {std::move(first), std::move(out_last)}; } template<ranges::input_range R1, ranges::random_access_range R2, class Comp = ranges::less, class Proj1 = std::identity, class Proj2 = std::identity> requires std::indirectly_copyable<ranges::iterator_t<R1>, ranges::iterator_t<R2>> && std::sortable<ranges::iterator_t<R2>, Comp, Proj2> && std::indirect_strict_weak_order<Comp, std::projected<ranges::iterator_t<R1>, Proj1>, std::projected<ranges::iterator_t<R2>, Proj2>> constexpr ranges::partial_sort_copy_result<ranges::borrowed_iterator_t<R1>, ranges::borrowed_iterator_t<R2>> operator()(R1&& r, R2&& result_r, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const { return (*this)(ranges::begin(r), ranges::end(r), ranges::begin(result_r), ranges::end(result_r), std::move(comp), std::move(proj1), std::move(proj2)); } }; inline constexpr partial_sort_copy_fn partial_sort_copy {}; |
[編輯] 示例
#include <algorithm> #include <forward_list> #include <functional> #include <iostream> #include <ranges> #include <string_view> #include <vector> void print(std::string_view rem, std::ranges::input_range auto const& v) { for (std::cout << rem; const auto& e : v) std::cout << e << ' '; std::cout << '\n'; } int main() { const std::forward_list source{4, 2, 5, 1, 3}; print("Write to the smaller vector in ascending order: ", ""); std::vector dest1{10, 11, 12}; print("const source list: ", source); print("destination range: ", dest1); std::ranges::partial_sort_copy(source, dest1); print("partial_sort_copy: ", dest1); print("Write to the larger vector in descending order:", ""); std::vector dest2{10, 11, 12, 13, 14, 15, 16}; print("const source list: ", source); print("destination range: ", dest2); std::ranges::partial_sort_copy(source, dest2, std::greater{}); print("partial_sort_copy: ", dest2); }
輸出
Write to the smaller vector in ascending order: const source list: 4 2 5 1 3 destination range: 10 11 12 partial_sort_copy: 1 2 3 Write to the larger vector in descending order: const source list: 4 2 5 1 3 destination range: 10 11 12 13 14 15 16 partial_sort_copy: 5 4 3 2 1 15 16
[編輯] 參閱
| (C++20) |
對一個範圍的前 N 個元素進行排序 (演算法函式物件) |
| (C++20) |
將一個範圍按升序排序 (演算法函式物件) |
| (C++20) |
對一個範圍的元素進行排序，同時保留相等元素之間的順序 (演算法函式物件) |
| (C++20) |
將一個最大堆轉換成一個按升序排序的元素範圍 (演算法函式物件) |
| (C++20) |
從一個元素範圍建立一個最大堆 (演算法函式物件) |
| (C++20) |
向一個最大堆新增一個元素 (演算法函式物件) |
| (C++20) |
從一個最大堆中移除最大的元素 (演算法函式物件) |
| 複製並部分排序一個範圍的元素 (函式模板) |
