列出不同字符组合的排列 [英] Listing permutations of different combination of characters

问题描述

我在这里找到最接近的SO主题:列出字符串的所有排列/整数

The closest SO topic I found is here: Listing all permutations of a string/integer

但是我将如何针对字符串中每个位置的不同字符集使用此功能呢?

But how would I make use of this for different sets of characters for each position in a string?

一个示例:我将字符串长度指定为"3".前两个位置应该是"a"或"b"，但最后一个位置应该是"1"或"2"，例如:

An example: I specify a string length of "3". The first two position should be either "a" or "b", but the last position should be either "1" or "2", e.g:

aa1
ba1
ab1
bb1
aa2
ab2
ba2
bb2

推荐答案

使用以下代码:

public static List<string> GenerateCombinations(char[][] characters)
{
    var combinations = new List<string>();
    GenerateCombinations(0, characters, new char[characters.GetLength(0)], combinations);
    return combinations;
}

private static void GenerateCombinations(int level, char[][] characters, char[] current, List<string> combinations)
{
    if (level == characters.GetLength(0))
    {
        combinations.Add(new string(current));
        return;
    }

    foreach (var character in characters[level])
    {
        current[level] = character;
        GenerateCombinations(level + 1, characters, current, combinations);
    }
}

使用示例:

public static void Main()
{
    var characters = new[]
                     {
                         new[] { 'a', 'b' },
                         new[] { 'a', 'b' },
                         new[] { '1', '2' }
                     };

    var combinations = GenerateCombinations(characters);
    foreach (var combination in combinations)
    {
        Console.WriteLine(combination);
    }
}

输出:

aa1
aa2
ab1
ab2
ba1
ba2
bb1
bb2

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