c# - C# 中的整数范围列表

Question

我有几个具有整数序列的类，这些序列在另一个类中注册，该类检查序列中的数字是否尚未使用。

序列是最连续的，从一个数字到另一个。

目前我一直在使用一个简单的列表，这意味着如果一个序列表示从 5000 到 15000，则列表中将有 10000 个元素。我想用更合适的东西来代替它，它可以在一个简单的元素中表示范围。

在我的特殊情况下，我还希望这些范围代表一个对象(序列起源的类)，这样当我查找一个数字时，我可以访问它的来源而不是通过每个类来查找查看它们是否包含我要查找的号码。

这是我的伪代码以及我期望的结果:

/* int is the integer type, while string is the "tag" object */
var animals = new IntRangeArray<int, string>();

animals.Add(1, "dog");
// [0] begin: 1, end: 1, object: "dog"

animals.Add(2, "dog");
// [0] begin: 1, end: 2, object: "dog"

/* AddRange with C#7.0 ValueTuple */
animals.AddRange((4,14), "dog");
// [0] begin: 1, end: 2, object: "dog"
// [1] begin: 4, end: 14, object: "dog"

animals.Add(3, "dog");
// [0] begin: 1, end: 14, object: "dog" 
/* All sequences have been merged because they are contiguous and have the same tag */

animals.AddRange( new int[]{ 15, 17, 18, 19 }, "dog");
// [0] begin: 1, end: 15, object: "dog"
// [1] begin: 17, end: 19, object: "dog"

animals.Add(16, "cat"); 
// [0] begin: 1, end: 15, object: "dog"
// [1] begin: 16, end: 16, object: "cat"
// [2] begin: 17, end: 19, object: "dog"

animals.Remove(8);
// [0] begin: 1, end: 7, object: "dog"
// [1] begin: 9, end: 15, object: "dog"
// [2] begin: 16, end: 16, object: "cat"
// [3] begin: 17, end: 18, object: "dog"

animals.At(11);
// struct { Begin = 9, End = 15, Tag = "dog" }

animals.RemoveWithTag("dog");
// [0] begin: 16, end: 16, object: "cat"

animals.TagOf(16);
// "cat"

我在 .NET Framework 中找不到任何实现此行为的类，所以我想知道如何实现它，或者是否已经存在任何实现。

Answer 1

对于这种事情，我通常最终会编写自己的类(class)。这是我会为此做的:

首先，Range 类，它有一个Begin、End 和Tag。它还有一些辅助方法来简化对重叠和相邻范围的查询，或进行不区分大小写的标签比较，以及输出字符串值:

class Range
{
    public int Begin { get; set; }
    public int End { get; set; }
    public string Tag { get; set; }

    public bool CombineWith(Range other)
    {
        Range combinedRange;
        if (TryCombine(this, other, out combinedRange))
        {
            this.Begin = combinedRange.Begin;
            this.End = combinedRange.End;
            return true;
        }

        return false;
    }

    public bool IsAdjacentTo(Range other)
    {
        return AreAdjacent(this, other);
    }

    public bool OverlapsWith(Range other)
    {
        return AreOverlapping(this, other);
    }

    public bool ContainsIndex(int index)
    {
        return this.Begin <= index && this.End >= index;
    }

    public bool TagEquals(string tag)
    {
        if (this.Tag == null) return tag == null;
        return this.Tag.Equals(tag, StringComparison.OrdinalIgnoreCase);
    }

    public static bool TryCombine(Range first, Range second, out Range combined)
    {
        combined = new Range();

        if (first == null || second == null) return false;
        if (!TagsEqual(first, second)) return false;
        if (!AreAdjacent(first, second) && !AreOverlapping(first, second)) return false;

        combined.Begin = Math.Min(first.Begin, second.Begin);
        combined.End = Math.Max(first.End, second.End);
        combined.Tag = first.Tag;

        return true;
    }

    public static bool AreAdjacent(Range first, Range second)
    {
        if (first == null || second == null) return false;
        if (!Range.TagsEqual(first, second)) return false;

        return (first.Begin == second.End + 1) ||
               (first.End == second.Begin - 1);
    }

    public static bool AreOverlapping(Range first, Range second)
    {
        if (first == null || second == null) return false;

        return (first.Begin >= second.Begin && first.Begin <= second.End) ||
               (first.End >= second.Begin && first.End <= second.End);
    }

    public static bool TagsEqual(Range first, Range second)
    {
        if (first == null || second == null) return false;
        return first.TagEquals(second.Tag);
    }

    public override string ToString()
    {
        return $"begin: {Begin}, end: {End}, tag: {Tag}";
    }
}

接下来是您的 IntRangeArray 类，它管理 Range 对象列表中项目的添加和删除:

class IntRangeArray
{
    private readonly List<Range> ranges = new List<Range>();

    public bool Add(int index, string tag)
    {
        return AddRange(index, index, tag);
    }

    public bool AddRange(IEnumerable<int> indexes, string tag)
    {
        if (indexes == null || string.IsNullOrWhiteSpace(tag)) return false;

        bool result = true;

        foreach (var index in indexes)
        {
            if (!Add(index, tag)) result = false;
        }

        return result;
    }

    public bool AddRange(Tuple<int, int> range, string tag)
    {
        return AddRange(range.Item1, range.Item2, tag);
    }

    public bool AddRange(int begin, int end, string tag)
    {
        if (begin < 0 || end < 0 || string.IsNullOrWhiteSpace(tag)) return false;

        var newRange = new Range {Begin = begin, End = end, Tag = tag};
        var overlappingRanges = ranges.Where(r => r.OverlapsWith(newRange)).ToList();
        var adjacentRanges = ranges.Where(r => r.IsAdjacentTo(newRange)).ToList();

        if (overlappingRanges.Any())
        {
            if (!overlappingRanges.All(r => r.TagEquals(newRange.Tag)))
            {
                return false;
            }

            foreach (var overlappingRange in overlappingRanges)
            {
                newRange.CombineWith(overlappingRange);
                ranges.Remove(overlappingRange);
            }
        }

        foreach (var adjacentRange in adjacentRanges)
        {
            newRange.CombineWith(adjacentRange);
            ranges.Remove(adjacentRange);
        }

        ranges.Add(newRange);
        return true;
    }

    public string At(int index)
    {
        var matchingRange = ranges.SingleOrDefault(r => r.ContainsIndex(index));
        return matchingRange?.ToString() ?? $"No item exists at {index}";
    }

    public void Remove(int index)
    {
        var matchingRange = ranges.SingleOrDefault(r => r.ContainsIndex(index));
        if (matchingRange == null) return;

        if (matchingRange.Begin == matchingRange.End)
        {
            ranges.Remove(matchingRange);
        }
        else if (index == matchingRange.Begin)
        {
            matchingRange.Begin += 1;
        }
        else if (index == matchingRange.End)
        {
            matchingRange.End -= 1;
        }
        else
        {
            // Split the range by creating a new one for the beginning
            var newRange = new Range
            {
                Begin = matchingRange.Begin,
                End = index - 1,
                Tag = matchingRange.Tag
            };

            matchingRange.Begin = index + 1;
            ranges.Add(newRange);
        }            
    }

    public void RemoveWithTag(string tag)
    {
        ranges.RemoveAll(r => r.TagEquals(tag));
    }

    public string TagOf(int index)
    {
        var matchingRange = ranges.SingleOrDefault(r => r.ContainsIndex(index));
        return matchingRange == null ? $"No item exists at {index}" : matchingRange.Tag;
    }

    public override string ToString()
    {
        if (ranges == null || !ranges.Any()) return "No items exist.";

        ranges.Sort((x, y) => x.Begin.CompareTo(y.Begin));
        var output = new StringBuilder();

        for(int i = 0; i < ranges.Count; i++)
        {
             output.AppendLine($"[{i}] {ranges[i]}");
        }

        return output.ToString();
    }
}

为了测试它，我刚刚复制并粘贴了上面的代码示例:

private static void Main()
{
    /* int is the integer type, while string is the "tag" object */
    var animals = new IntRangeArray();

    animals.Add(1, "dog");
    Console.WriteLine(animals);

    animals.Add(2, "dog");
    Console.WriteLine(animals);

    /* AddRange with C#7.0 ValueTuple */
    animals.AddRange(Tuple.Create(4, 14), "dog");
    Console.WriteLine(animals);

    animals.Add(3, "dog");
    Console.WriteLine(animals);

    animals.AddRange(new int[] { 15, 17, 18, 19 }, "dog");
    Console.WriteLine(animals);

    animals.Add(16, "cat");
    Console.WriteLine(animals);

    animals.Remove(8);
    Console.WriteLine(animals);

    Console.WriteLine(animals.At(11));

    animals.RemoveWithTag("dog");
    Console.WriteLine(animals);

    Console.WriteLine(animals.TagOf(16));

    Console.WriteLine("\nDone!\nPress any key to exit...");
    Console.ReadKey();
}

输出如您所料(除了有一项不同，但那是您这边的错误):