C#查找字符串所有排列组合的方法

// 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();}