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"].
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
分析：暴力搜索所有结果。
代码如下：
1 class Solution { 2 public: 3 const vector<string> keyboards{" ","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"}; 4 vector<string> letterCombinations(string digits) { 5 vector<string> res; 6 string path; 7 dfs(res,path,digits,0); 8 return res; 9 } 10 void dfs(vector<string> & res, string & path, string digits, int k){ 11 if(digits.size() == k){ 12 res.push_back(path); 13 return; 14 } 15 for(auto c: keyboards[digits[k]-‘0‘]){ 16 path.push_back(c); 17 dfs(res,path,digits,k+1); 18 path.pop_back(); 19 } 20 } 21 };
Letter Combinations of a Phone Number,布布扣,bubuko.com
Letter Combinations of a Phone Number
原文：http://www.cnblogs.com/Kai-Xing/p/3917841.html