diff --git a/osu.Game/Beatmaps/ControlPoints/ControlPointInfo.cs b/osu.Game/Beatmaps/ControlPoints/ControlPointInfo.cs index f8e72a1e34..4fc77084d6 100644 --- a/osu.Game/Beatmaps/ControlPoints/ControlPointInfo.cs +++ b/osu.Game/Beatmaps/ControlPoints/ControlPointInfo.cs @@ -230,32 +230,12 @@ namespace osu.Game.Beatmaps.ControlPoints { ArgumentNullException.ThrowIfNull(list); - if (list.Count == 0) - return null; + int index = BinarySearchUtils.BinarySearch(list, time, c => c.Time, EqualitySelection.Rightmost); - if (time < list[0].Time) - return null; + if (index < 0) + index = ~index - 1; - if (time >= list[^1].Time) - return list[^1]; - - int l = 0; - int r = list.Count - 2; - - while (l <= r) - { - int pivot = l + ((r - l) >> 1); - - if (list[pivot].Time < time) - l = pivot + 1; - else if (list[pivot].Time > time) - r = pivot - 1; - else - return list[pivot]; - } - - // l will be the first control point with Time > time, but we want the one before it - return list[l - 1]; + return index >= 0 ? list[index] : null; } /// diff --git a/osu.Game/Utils/BinarySearchUtils.cs b/osu.Game/Utils/BinarySearchUtils.cs new file mode 100644 index 0000000000..de5fc101d5 --- /dev/null +++ b/osu.Game/Utils/BinarySearchUtils.cs @@ -0,0 +1,99 @@ +// Copyright (c) ppy Pty Ltd . Licensed under the MIT Licence. +// See the LICENCE file in the repository root for full licence text. + +using System; +using System.Collections.Generic; + +namespace osu.Game.Utils +{ + public class BinarySearchUtils + { + /// + /// Finds the index of the item in the sorted list which has its property equal to the search term. + /// If no exact match is found, the complement of the index of the first item greater than the search term will be returned. + /// + /// The type of the items in the list to search. + /// The type of the property to perform the search on. + /// The list of items to search. + /// The query to find. + /// Function that maps an item in the list to its index property. + /// Determines which index to return if there are multiple exact matches. + /// The index of the found item. Will return the complement of the index of the first item greater than the search query if no exact match is found. + public static int BinarySearch(IReadOnlyList list, T2 searchTerm, Func termFunc, EqualitySelection equalitySelection = EqualitySelection.FirstFound) + { + int n = list.Count; + + if (n == 0) + return -1; + + var comparer = Comparer.Default; + + if (comparer.Compare(searchTerm, termFunc(list[0])) == -1) + return -1; + + if (comparer.Compare(searchTerm, termFunc(list[^1])) == 1) + return ~n; + + int min = 0; + int max = n - 1; + bool equalityFound = false; + + while (min <= max) + { + int mid = min + (max - min) / 2; + T2 midTerm = termFunc(list[mid]); + + switch (comparer.Compare(midTerm, searchTerm)) + { + case 0: + equalityFound = true; + + switch (equalitySelection) + { + case EqualitySelection.Leftmost: + max = mid - 1; + break; + + case EqualitySelection.Rightmost: + min = mid + 1; + break; + + default: + case EqualitySelection.FirstFound: + return mid; + } + + break; + + case 1: + max = mid - 1; + break; + + case -1: + min = mid + 1; + break; + } + } + + if (!equalityFound) return ~min; + + switch (equalitySelection) + { + case EqualitySelection.Leftmost: + return min; + + case EqualitySelection.Rightmost: + return min - 1; + } + + return ~min; + } + } + + public enum EqualitySelection + { + FirstFound, + Leftmost, + Rightmost + } +}