Letter Combinations of a Phone Number

Given a digit string, return all possible letter combinations that the number could represent.

A mapping of digit to letters (just like on the telephone buttons) is given below.

Input:Digit string "23"
Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

  vector<string> letterCombinations(string digits) {
       string trans[] = {"", " ", "abc", "def", "ghi", "jkl",
         "mno", "pqrs", "tuv", "wxyz"};
       vector<string> set;
       string seq;
       Generater(trans, digits, , seq, set);
       return set;
     }
     void Generater(string trans[], string& digits,
       int deep, string& result, vector<string>& set)
     {
       if(deep == digits.size())
       {
         set.push_back(result);
         return;
       }
       int curDig = digits[deep] - ;
       for(int i =; i < trans[curDig].size(); i++)
       {
         result.push_back(trans[curDig][i]);
         Generater(trans, digits, deep+, result, set);
         result.resize(result.size() -);
       }
     }