C#查找字符串的所有排列组合

// 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();

        }</string></string>