Leetcode 17. Letter Combinations of a Phone Number(水)

17. Letter Combinations of a Phone Number

Medium

Given a string containing digits from 2-9 inclusive, 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. Note that 1 does not map to any letters.

Example:

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

Note:

Although the above answer is in lexicographical order, your answer could be in any order you want.

 class Solution {
 public:
     vector<string> letterCombinations(string digits) {
         map<char,string> test;
         test[''] = "abc";
         test[''] = "def";
         test[''] = "ghi";
         test[''] = "jkl";
         test[''] = "mno";
         test[''] = "pqrs";
         test[''] = "tuv";
         test[''] = "wxyz";
         vector<string> fa_;
         vector<string> chil_;
         fa_.push_back("");
         for(int i = ; i < digits.length(); i++){
             chil_.clear();
             for(int j = ; j < fa_.size(); j++){
                 //printf("%d %s",test[digits[i]].length());
                 for(int k = ; k < test[digits[i]].length(); k++){
                     //printf("%s",test[digits[i]][k]);
                     chil_.push_back(fa_[j]+test[digits[i]][k]);
                 }
             }
             fa_ = chil_;
         }
         return chil_;
     }
 };