我过去几次需要此功能，而afaik做到这一点最简单的方法是
- 创建并填充一个可通过索引访问的SortedList
- 在IList
SortedList.Keys 上使用合适的*）BinarySearch方法 - 通过IList
SortedList.Values 访问该值 - 将2.和3.包装成扩展方法
IEnumerable<KeyValuePair<K, V>> Tail(this SortedList<K, V> list, K fromKey, bool inclusive = true)
张贴在这里的答案，所以我可以复制和粘贴从此以后我只是执行Head
和Tail
和附加的代码-见下文。此外，我还添加了TryGetCeiling / Floor / Higher / LowerValue方法-从Java的NavigableMap派生的名称，为需要它们的任何人添加TryGet Key和TryGet Entry都非常简单。
*）不幸的是，.Net自己的实现仅适用于
List，不适用于
IList。真是浪费。此外，请确保使用
~x未找到该物品时会返回的物品，例如我链接到的物品。
public static class SortedListEx{ public static IEnumerable<KeyValuePair<K, V>> Head<K, V>( this SortedList<K, V> list, K toKey, bool inclusive = true) { https://stackoverflow.com/a/2948872/709537 BinarySearch var binarySearchResult = list.Keys.BinarySearch(toKey); if (binarySearchResult < 0) binarySearchResult = ~binarySearchResult; else if (inclusive) binarySearchResult++; return System.Linq.Enumerable.Take(list, binarySearchResult); } public static IEnumerable<KeyValuePair<K, V>> Tail<K, V>( this SortedList<K, V> list, K fromKey, bool inclusive = true) { https://stackoverflow.com/a/2948872/709537 BinarySearch var binarySearchResult = list.Keys.BinarySearch(fromKey); if (binarySearchResult < 0) binarySearchResult = ~binarySearchResult; else if (!inclusive) binarySearchResult++; return new ListOffsetEnumerable<K, V>(list, binarySearchResult); } public static bool TryGetCeilingValue<K, V>( this SortedList<K, V> list, K key, out V value) { var binarySearchResult = list.Keys.BinarySearch(key); if (binarySearchResult < 0) binarySearchResult = ~binarySearchResult; if (binarySearchResult >= list.Count) { value = default(V); return false; } value = list.Values[binarySearchResult]; return true; } public static bool TryGetHigherValue<K, V>( this SortedList<K, V> list, K key, out V value) { var binarySearchResult = list.Keys.BinarySearch(key); if (binarySearchResult < 0) binarySearchResult = ~binarySearchResult; else binarySearchResult++; if (binarySearchResult >= list.Count) { value = default(V); return false; } value = list.Values[binarySearchResult]; return true; } public static bool TryGetFloorValue<K, V>( this SortedList<K, V> list, K key, out V value) { var binarySearchResult = list.Keys.BinarySearch(key); if (binarySearchResult < 0) binarySearchResult = ~binarySearchResult; else binarySearchResult++; if (binarySearchResult >= list.Count) { value = default(V); return false; } value = list.Values[binarySearchResult]; return true; } public static bool TryGetLowerValue<K, V>( this SortedList<K, V> list, K key, out V value) { var binarySearchResult = list.Keys.BinarySearch(key); if (binarySearchResult < 0) binarySearchResult = ~binarySearchResult; if (binarySearchResult >= list.Count) { value = default(V); return false; } value = list.Values[binarySearchResult]; return true; } class ListOffsetEnumerable<K, V> : IEnumerable<KeyValuePair<K, V>> { private readonly SortedList<K, V> _sortedList; private readonly int _offset; public ListOffsetEnumerable(SortedList<K, V> sortedList, int offset) { _sortedList = sortedList; _offset = offset; } public IEnumerator<KeyValuePair<K, V>> GetEnumerator() { return new ListOffsetEnumerator<K, V>(_sortedList, _offset); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } } class ListOffsetEnumerator<K, V> : IEnumerator<KeyValuePair<K, V>> { private readonly SortedList<K, V> _sortedList; private int _index; public ListOffsetEnumerator(SortedList<K, V> sortedList, int offset) { _sortedList = sortedList; _index = offset - 1; } public bool MoveNext() { if (_index >= _sortedList.Count) return false; _index++; return _index < _sortedList.Count; } public KeyValuePair<K, V> Current { get { return new KeyValuePair<K, V>( _sortedList.Keys[_index], _sortedList.Values[_index]); } } object IEnumerator.Current { get { return Current; } } public void Dispose() { } public void Reset() { throw new NotSupportedException(); } }}这是一个简单的测试
SortedList<int, int> l = new SortedList<int, int> { { 1, 1 }, { 3, 3 }, { 4, 4 } };for (int i = 0; i <= 5; i++){ Console.WriteLine("{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( " +i+ ", true): " + string.Join(", ", l.Head(i, true))); Console.WriteLine("{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( " +i+ ", false): " + string.Join(", ", l.Head(i, false)));}for (int i = 0; i <= 5; i++){ Console.WriteLine("{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( " +i+ ", true): " + string.Join(", ", l.Tail(i, true))); Console.WriteLine("{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( " +i+ ", false): " + string.Join(", ", l.Tail(i, false)));}打印以下内容：
{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 0, true):{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 0, false):{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 1, true): [1, 1]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 1, false):{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 2, true): [1, 1]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 2, false): [1, 1]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 3, true): [1, 1], [3, 3]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 3, false): [1, 1]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 4, true): [1, 1], [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 4, false): [1, 1], [3, 3]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 5, true): [1, 1], [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Head( 5, false): [1, 1], [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 0, true): [1, 1], [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 0, false): [1, 1], [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 1, true): [1, 1], [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 1, false): [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 2, true): [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 2, false): [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 3, true): [3, 3], [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 3, false): [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 4, true): [4, 4]{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 4, false):{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 5, true):{ { 1, 1 }, { 3, 3 }, { 4, 4 } }.Tail( 5, false):
