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SPDX License Identifiers are a more compact / standardized way of representing file license information. See: https://spdx.dev/resources/use/#identifiers This was done with the `ambr` search and replace tool. ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
131 lines
3.4 KiB
C++
131 lines
3.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/StdLibExtras.h>
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namespace AK {
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/* This is a dual pivot quick sort. It is quite a bit faster than the single
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* pivot quick_sort below. The other quick_sort below should only be used when
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* you are stuck with simple iterators to a container and you don't have access
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* to the container itself.
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*/
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template<typename Collection, typename LessThan>
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void dual_pivot_quick_sort(Collection& col, int start, int end, LessThan less_than)
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{
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if (start >= end) {
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return;
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}
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int left_pointer, right_pointer;
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if (!less_than(col[start], col[end])) {
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swap(col[start], col[end]);
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}
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int j = start + 1;
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int k = start + 1;
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int g = end - 1;
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auto&& left_pivot = col[start];
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auto&& right_pivot = col[end];
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while (k <= g) {
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if (less_than(col[k], left_pivot)) {
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swap(col[k], col[j]);
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j++;
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} else if (!less_than(col[k], right_pivot)) {
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while (!less_than(col[g], right_pivot) && k < g) {
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g--;
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}
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swap(col[k], col[g]);
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g--;
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if (less_than(col[k], left_pivot)) {
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swap(col[k], col[j]);
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j++;
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}
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}
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k++;
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}
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j--;
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g++;
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swap(col[start], col[j]);
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swap(col[end], col[g]);
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left_pointer = j;
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right_pointer = g;
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dual_pivot_quick_sort(col, start, left_pointer - 1, less_than);
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dual_pivot_quick_sort(col, left_pointer + 1, right_pointer - 1, less_than);
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dual_pivot_quick_sort(col, right_pointer + 1, end, less_than);
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}
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template<typename Iterator, typename LessThan>
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void single_pivot_quick_sort(Iterator start, Iterator end, LessThan less_than)
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{
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for (;;) {
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int size = end - start;
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if (size <= 1)
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return;
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int pivot_point = size / 2;
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if (pivot_point)
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swap(*(start + pivot_point), *start);
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auto&& pivot = *start;
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int i = 1;
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for (int j = 1; j < size; ++j) {
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if (less_than(*(start + j), pivot)) {
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swap(*(start + j), *(start + i));
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++i;
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}
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}
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swap(*start, *(start + i - 1));
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// Recur into the shorter part of the remaining data
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// to ensure a stack depth of at most log(n).
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if (i > size / 2) {
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single_pivot_quick_sort(start + i, end, less_than);
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end = start + i - 1;
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} else {
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single_pivot_quick_sort(start, start + i - 1, less_than);
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start = start + i;
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}
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}
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}
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template<typename Iterator>
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void quick_sort(Iterator start, Iterator end)
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{
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single_pivot_quick_sort(start, end, [](auto& a, auto& b) { return a < b; });
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}
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template<typename Iterator, typename LessThan>
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void quick_sort(Iterator start, Iterator end, LessThan less_than)
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{
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single_pivot_quick_sort(start, end, move(less_than));
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}
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template<typename Collection, typename LessThan>
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void quick_sort(Collection& collection, LessThan less_than)
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{
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dual_pivot_quick_sort(collection, 0, collection.size() - 1, move(less_than));
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}
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template<typename Collection>
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void quick_sort(Collection& collection)
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{
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dual_pivot_quick_sort(collection, 0, collection.size() - 1,
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[](auto& a, auto& b) { return a < b; });
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}
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}
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using AK::quick_sort;
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