借鉴微博：https://blog.csdn.net/zhifeiya/article/details/42919047

核心代码：

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
public class Descartes
{
/// <summary>
/// 笛卡尔积
/// </summary>
/// <param name="dimvalue">将每个维度的集合的元素视为List<string>,多个集合构成List<List<string>> dimvalue作为输入</param>
/// <param name="result">将多维笛卡尔乘积的结果放到List<string> result之中作为输出</param>
/// <param name="layer">int layer 只是两个中间过程的参数携带变量</param>
/// <param name="curstring"> string curstring只是两个中间过程的参数携带变量,传递""就行</param>
public static void run(List<List<string>> dimvalue, List<string> result, int layer=0, string curstring="")
{
if (layer < dimvalue.Count - 1)
{
if (dimvalue[layer].Count == 0)
run(dimvalue, result, layer + 1, curstring);
else
{
for (int i = 0; i < dimvalue[layer].Count; i++)
{
StringBuilder s1 = new StringBuilder();
s1.Append(curstring);
s1.Append(dimvalue[layer][i]);
run(dimvalue, result, layer + 1, s1.ToString());
}
}
}
else if (layer == dimvalue.Count - 1)
{
if (dimvalue[layer].Count == 0) result.Add(curstring);
else
{
for (int i = 0; i < dimvalue[layer].Count; i++)
{
result.Add(curstring + dimvalue[layer][i]);
}
}
}
}
}

这里自己做个记录，