C#或滑动窗口枚举器中的成对迭代

如果我有一个IEnumerable像:

string[] items = new string[] { "a", "b", "c", "d" };

我想循环通过所有连续项目(大小为2的滑动窗口).这将是

("a","b"), ("b", "c"), ("c", "d")

我的解决方案就是这样

    public static IEnumerable> Pairs(IEnumerable enumerable) {
        IEnumerator e = enumerable.GetEnumerator(); e.MoveNext();
        T current = e.Current;
        while ( e.MoveNext() ) {
            T next = e.Current;
            yield return new Pair(current, next);
            current = next;
        }
    }

 // used like this :
 foreach (Pair pair in IterTools.Pairs(items)) {
    System.Out.PrintLine("{0}, {1}", pair.First, pair.Second)
 }

当我编写这段代码时,我想知道.NET框架中是否已经存在执行相同操作的函数,并且它不仅适用于对,而且适用于任何大小的元组.恕我直言应该有一个很好的方法来做这种滑动窗口操作.

我使用C#2.0,我可以想象使用C#3.0(w/LINQ)有更多(更好)的方法来做到这一点,但我主要对C#2.0解决方案感兴趣.不过,我也很欣赏C#3.0解决方案.

In .NET 4 this becomes even easier:-

var input = new[] { "a", "b", "c", "d", "e", "f" };
var result = input.Zip(input.Skip(1), (a, b) => Tuple.Create(a, b));

而不是需要一个元组(对)类型,为什么不接受一个选择器:

public static IEnumerable Pairwise(this IEnumerable source, Func resultSelector)
{
    TSource previous = default(TSource);

    using (var it = source.GetEnumerator())
    {
        if (it.MoveNext())
            previous = it.Current;

        while (it.MoveNext())
            yield return resultSelector(previous, previous = it.Current);
    }
}

如果您愿意,可以跳过中间对象:

string[] items = new string[] { "a", "b", "c", "d" };
var pairs = items.Pairwise((x, y) => string.Format("{0},{1}", x, y));

foreach(var pair in pairs)
    Console.WriteLine(pair);

或者您可以使用匿名类型:

var pairs = items.Pairwise((x, y) => new { First = x, Second = y });

最简单的方法是使用ReactiveExtensions

using System.Reactive;
using System.Reactive.Linq;

并使自己成为一个扩展方法,以便将它们放在一起

public static IEnumerable> Buffer(this IEnumerable seq, int bufferSize, int stepSize)
{
    return seq.ToObservable().Buffer(bufferSize, stepSize).ToEnumerable();
}

public class SlidingWindowCollection : ICollection
{
    private int _windowSize;
    private Queue _source;

    public SlidingWindowCollection(int windowSize)
    {
        _windowSize = windowSize;
        _source = new Queue(windowSize);
    }

    public void Add(T item)
    {
        if (_source.Count == _windowSize)
        {
            _source.Dequeue();
        }
        _source.Enqueue(item);
    }

    public void Clear()
    {
        _source.Clear();
    }

    ...and just keep forwarding all other ICollection methods to _source.
}

int pairSize = 2;
var slider = new SlidingWindowCollection(pairSize);
foreach(var item in items)
{
    slider.Add(item);
    Console.WriteLine(string.Join(", ", slider));
}