申请& quot;加入"的最佳方法是什么?方法通常类似于String.Join(...)的工作方式? [英] What's the best way to apply a "Join" method generically similar to how String.Join(...) works?

问题描述

如果我有一个字符串数组，例如:var array = new[] { "the", "cat", "in", "the", "hat" }，并且我想将它们连接在一起，并且每个单词之间都有一个空格，那么我可以简单地调用String.Join(" ", array).

If I have a string array, for example: var array = new[] { "the", "cat", "in", "the", "hat" }, and I want to join them with a space between each word I can simply call String.Join(" ", array).

但是，说我有一个整数数组的数组(就像我可以有一个字符数组的数组一样).我想将它们组合成一个大数组(展平它们)，但同时在每个数组之间插入一个值.

But, say I had an array of integer arrays (just like I can have an array of character arrays). I want to combine them into one large array (flatten them), but at the same time insert a value between each array.

var arrays = new[] { new[] { 1, 2, 3 }, new[] { 4, 5, 6 }, new { 7, 8, 9 }};

var result = SomeJoin(0, arrays); // result = { 1, 2, 3, 0, 4, 5, 6, 0, 7, 8, 9 }

我写了一些东西，但是很丑陋，我敢肯定有更好，更干净的方法.也许更有效率?

I wrote something up, but it is very ugly, and I'm sure that there is a better, cleaner way. Maybe more efficient?

var result = new int[arrays.Sum(a => a.Length) + arrays.Length - 1];

int offset = 0;
foreach (var array in arrays)
{
     Buffer.BlockCopy(array, 0, result, offset, b.Length);
     offset += array.Length;

     if (offset < result.Length)
     {
         result[offset++] = 0;
     }
}

也许这是最有效的?我不知道...只是看看是否有更好的方法.我以为LINQ可能会解决这个问题，但可惜我没有看到我需要的任何东西.

Perhaps this is the most efficient? I don't know... just seeing if there is a better way. I thought maybe LINQ would solve this, but sadly I don't see anything that is what I need.

推荐答案

您可以通过以下方式一般地加入"序列:

You can generically "join" sequences via:

public static IEnumerable<T> Join<T>(T separator, IEnumerable<IEnumerable<T>> items)
{
    var sep = new[] {item};
    var first = items.FirstOrDefault();
    if (first == null)
        return Enumerable.Empty<T>();
    else
        return first.Concat(items.Skip(1).SelectMany(i => sep.Concat(i)));      
}

这适用于您的代码:

var arrays = new[] { new[] { 1, 2, 3 }, new[] { 4, 5, 6 }, new { 7, 8, 9 }};
var result = Join(0, arrays); // result = { 1, 2, 3, 0, 4, 5, 6, 0, 7, 8, 9 }

此处的优点是，它将与任何IEnumerable<IEnumerable<T>>一起使用，并且不仅限于列表或数组.请注意，这将在两个空序列之间插入一个分隔符，但是如果需要，可以修改该行为.

The advantage here is that this will work with any IEnumerable<IEnumerable<T>>, and isn't restricted to lists or arrays. Note that this will insert a separate in between two empty sequences, but that behavior could be modified if desired.

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