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158 lines
5.2 KiB
C#
158 lines
5.2 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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#nullable disable
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using System;
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using System.Collections.Generic;
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using System.Diagnostics.Contracts;
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namespace osu.Game.Rulesets.Mania.MathUtils
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{
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/// <summary>
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/// Provides access to .NET4.0 unstable sorting methods.
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/// </summary>
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/// <remarks>
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/// Source: https://referencesource.microsoft.com/#mscorlib/system/collections/generic/arraysorthelper.cs
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/// Copyright (c) Microsoft Corporation. All rights reserved.
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/// </remarks>
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internal static class LegacySortHelper<T>
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{
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private const int quick_sort_depth_threshold = 32;
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public static void Sort(T[] keys, IComparer<T> comparer)
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{
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if (keys == null)
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throw new ArgumentNullException(nameof(keys));
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if (keys.Length == 0)
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return;
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comparer ??= Comparer<T>.Default;
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depthLimitedQuickSort(keys, 0, keys.Length - 1, comparer, quick_sort_depth_threshold);
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}
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private static void depthLimitedQuickSort(T[] keys, int left, int right, IComparer<T> comparer, int depthLimit)
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{
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do
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{
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if (depthLimit == 0)
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{
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heapsort(keys, left, right, comparer);
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return;
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}
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int i = left;
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int j = right;
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// pre-sort the low, middle (pivot), and high values in place.
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// this improves performance in the face of already sorted data, or
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// data that is made up of multiple sorted runs appended together.
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int middle = i + ((j - i) >> 1);
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swapIfGreater(keys, comparer, i, middle); // swap the low with the mid point
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swapIfGreater(keys, comparer, i, j); // swap the low with the high
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swapIfGreater(keys, comparer, middle, j); // swap the middle with the high
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T x = keys[middle];
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do
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{
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while (comparer.Compare(keys[i], x) < 0) i++;
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while (comparer.Compare(x, keys[j]) < 0) j--;
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Contract.Assert(i >= left && j <= right, "(i>=left && j<=right) Sort failed - Is your IComparer bogus?");
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if (i > j) break;
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if (i < j)
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{
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(keys[i], keys[j]) = (keys[j], keys[i]);
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}
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i++;
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j--;
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} while (i <= j);
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// The next iteration of the while loop is to "recursively" sort the larger half of the array and the
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// following calls recrusively sort the smaller half. So we subtrack one from depthLimit here so
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// both sorts see the new value.
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depthLimit--;
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if (j - left <= right - i)
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{
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if (left < j) depthLimitedQuickSort(keys, left, j, comparer, depthLimit);
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left = i;
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}
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else
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{
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if (i < right) depthLimitedQuickSort(keys, i, right, comparer, depthLimit);
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right = j;
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}
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} while (left < right);
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}
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private static void heapsort(T[] keys, int lo, int hi, IComparer<T> comparer)
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{
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Contract.Requires(keys != null);
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Contract.Requires(comparer != null);
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Contract.Requires(lo >= 0);
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Contract.Requires(hi > lo);
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Contract.Requires(hi < keys.Length);
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int n = hi - lo + 1;
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for (int i = n / 2; i >= 1; i = i - 1)
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{
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downHeap(keys, i, n, lo, comparer);
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}
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for (int i = n; i > 1; i = i - 1)
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{
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swap(keys, lo, lo + i - 1);
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downHeap(keys, 1, i - 1, lo, comparer);
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}
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}
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private static void downHeap(T[] keys, int i, int n, int lo, IComparer<T> comparer)
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{
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Contract.Requires(keys != null);
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Contract.Requires(comparer != null);
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Contract.Requires(lo >= 0);
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Contract.Requires(lo < keys.Length);
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T d = keys[lo + i - 1];
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while (i <= n / 2)
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{
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int child = 2 * i;
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if (child < n && comparer.Compare(keys[lo + child - 1], keys[lo + child]) < 0)
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{
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child++;
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}
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if (!(comparer.Compare(d, keys[lo + child - 1]) < 0))
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break;
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keys[lo + i - 1] = keys[lo + child - 1];
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i = child;
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}
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keys[lo + i - 1] = d;
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}
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private static void swap(T[] a, int i, int j)
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{
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if (i != j)
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(a[i], a[j]) = (a[j], a[i]);
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}
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private static void swapIfGreater(T[] keys, IComparer<T> comparer, int a, int b)
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{
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if (a != b)
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{
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if (comparer.Compare(keys[a], keys[b]) > 0)
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(keys[a], keys[b]) = (keys[b], keys[a]);
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}
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}
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}
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}
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