C#查找字符串的所有排列組合

C#查找字符串的所有排列組合

// 1. remove first char
// 2. find permutations of the rest of chars
// 3. Attach the first char to each of those permutations.
//     3.1  for each permutation, move firstChar in all indexes to produce even more permutations.
// 4. Return list of possible permutations.

public string[] FindPermutations(string word)
        {
            if (word.Length == 2)
            {
                char[] _c = word.ToCharArray();
                string s = new string(new char[] { _c[1], _c[0] });
                return new string[]
                {
                    word,
                    s
                };
            }

        List<string> _result = new List<string>();

        string[] _subsetPermutations = FindPermutations(word.Substring(1));
        char _firstChar = word[0];
        foreach (string s in _subsetPermutations)
        {
            string _temp = _firstChar.ToString() + s;
            _result.Add(_temp);
            char[] _chars = _temp.ToCharArray();
            for (int i = 0; i < _temp.Length - 1; i++)
            {
                char t = _chars[i];
                _chars[i] = _chars[i + 1];
                _chars[i + 1] = t;
                string s2 = new string(_chars);
                _result.Add(s2);
            }
        }
        return _result.ToArray();
    }           </pre>