c# - 如何使用 LINQ 将多级元组列表拆分为多级值列表？

Question

我有一个 List<List<Tuple<int, int, int>>>变量，我想把它分成三个 List<List<int>>秒。我已经可以像这样枚举列表三次:

List<List<Tuple<int, int, int>>> tuples = ...
List<List<int>> a = tuples.Select(x => x.Select(y => y.Item1).ToList()).ToList();
List<List<int>> b = tuples.Select(x => x.Select(y => y.Item2).ToList()).ToList();
List<List<int>> c = tuples.Select(x => x.Select(y => y.Item3).ToList()).ToList();

但是，我可以使用 LINQ 一次创建所有三个列表吗？像这样的东西:

Tuple<List<List<int>>, List<List<int>>, List<List<int>>> splitted = tuples.Magic(...);

编辑:(这是在tymtam和Mong Zhu发布他们的答案后添加的)

更清楚地说，稍后当我说“马上”时，我指的是性能。我真的不在乎结果的实际类型，我也不痴迷于单行完成。

性能方面的比较:

这是我的代码，用于比较拆分 1000 个包含 1000 个元组的列表，(50 次调用，4000 个样本/秒):

private void Split_Loop(List<List<Tuple<int, int, int>>> tuples)
{
    List<List<int>> a = new List<List<int>>(tuples.Count);
    List<List<int>> b = new List<List<int>>(tuples.Count);
    List<List<int>> c = new List<List<int>>(tuples.Count);
    for (int i = 0; i < tuples.Count; i++)
    {
        int n = tuples[i].Count;
        List<int> l1 = new List<int>(n);
        a.Add(l1);
        List<int> l2 = new List<int>(n);
        b.Add(l2);
        List<int> l3 = new List<int>(n);
        c.Add(l3);

        for (int j = 0; j < n; j++)
        {
            l1.Add(tuples[i][j].Item1);
            l2.Add(tuples[i][j].Item2);
            l3.Add(tuples[i][j].Item3);
        }
    }
}
private void Split_Linq3(List<List<Tuple<int, int, int>>> tuples)
{
    List<List<int>> a = tuples.Select(x => x.Select(y => y.Item1).ToList()).ToList();
    List<List<int>> b = tuples.Select(x => x.Select(y => y.Item2).ToList()).ToList();
    List<List<int>> c = tuples.Select(x => x.Select(y => y.Item3).ToList()).ToList();
}
private void Split_tymtam(List<List<Tuple<int, int, int>>> tuples)
{
    IEnumerable<List<List<int>>> a = new Func<Tuple<int, int, int>, int>[]
        { t => t.Item1, t => t.Item2, t => t.Item3 }.
            Select(f => tuples.Select(x => x.Select(f).ToList()).ToList());
    List<List<List<int>>> b = a.ToList();
}
private void Split_Mong(List<List<Tuple<int, int, int>>> tuples)
{
    Func<List<List<Tuple<int, int, int>>>, Func<Tuple<int, int, int>, int>, List<List<int>>> selectorGen = (x, t) => x.Select(y => y.Select(t).ToList()).ToList();
    Tuple<List<List<int>>, List<List<int>>, List<List<int>>> splitted = Tuple.Create(
            selectorGen(tuples, t => t.Item1),
            selectorGen(tuples, t => t.Item2),
            selectorGen(tuples, t => t.Item3));
}
private void button3_Click(object sender, EventArgs e)
{
    int outer = 1000;
    int inner = 1000;
    List<List<Tuple<int, int, int>>> tuples = new List<List<Tuple<int, int, int>>>(outer);
    for (int i = 0; i < outer; i++)
    {
        List<Tuple<int, int, int>> list = new List<Tuple<int, int, int>>(inner);
        tuples.Add(list);
        for (int j = 0; j < inner; j++)
        {
            Tuple<int, int, int> tuple = new Tuple<int, int, int>(i + j + 1, i + j + 2, i + j + 3);
            list.Add(tuple);
        }
    }
    for (int i = 0; i < 50; i++)
    {
        Split_Loop(tuples);
        Split_Linq3(tuples);
        Split_tymtam(tuples);
        Split_Mong(tuples);
    }
}

结果如下:

Answer 1

这是我能做的最好的了:

IEnumerable<List<List<int>>> myLists = new Func<Tuple<int, int, int>, int>[] 
            { t => t.Item1, t => t.Item2, t => t.Item3 }
           .Select(f => tuples.Select(x => x.Select(f).ToList()).ToList());