c# - 如何制作一组新词典，其中包含以列表为值的词典中的所有可能组合

Question

我需要用一个字符串键和一个字符串列表作为值的字典，并找到它可以进行的所有组合。 例如:

var myDictionary = new Dictionary<string, List<string>>
{
    {"X", new List<string> {"x", "y", "z"}},
    {"Y", new List<string> {"x", "y"}},
    {"Z", new List<string> {"a", "b"}}
};

将转化为:

{X: x, Y: x, Z: a}
{X: x, Y: x, Z: b}
{X: x, Y: y, Z: a}
{X: x, Y: y, Z: b}
{X: y, Y: x, Z: a}
{X: y, Y: x, Z: b}
{X: y, Y: y, Z: a}
{X: y, Y: y, Z: b}
{X: z, Y: x, Z: a}
{X: z, Y: x, Z: b}
{X: z, Y: y, Z: a}
{X: z, Y: y, Z: b}

我怎样才能以最聪明的方式做到这一点？

Answer 1

这样做怎么样？

var combinations =
    from x in myDictionary["X"]
    from y in myDictionary["Y"]
    from z in myDictionary["Z"]
    select new Dictionary<string, string>()
    {
        { "X", x },
        { "Y", y },
        { "Z", z },
    };

我得到这个结果:

---

经过进一步思考，这里有一种方法可以计算字典中任意数量的元素(即不仅仅是“X”、“Y”和“Z”。)

Func<
    Dictionary<string, string>,
    Dictionary<string, string>,
    Dictionary<string, string>> merge = (d1, d2) =>
{
    var d = new Dictionary<string, string>(d1);
    foreach (var kv in d2)
    {
        d.Add(kv.Key, kv.Value);
    }
    return d;
};

var combinations =
    myDictionary
        .Select(x =>
            x.Value.Select(v =>
                new Dictionary<string, string>()
                {
                    { x.Key, v }
                }))
        .Aggregate((xs, vs) =>
            from x in xs
            from v in vs
            select merge(x, v));