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.

思路：

又是dfs的题目，dfs的时候，注意string一定要清除本次添加的元素。

题解：

class Solution {public:    vector
      
        res;    string tmp;    void dfs(string digits, int index, string board[]) {        if(index==digits.size()) {            res.push_back(tmp);            return;        }        string str = board[digits[index]-'0'];        for(int i=0;i
       
         letterCombinations(string digits) {        string board[] = {
    "0", "1", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz",};        dfs(digits,0, board);        return res;    }};
       
      

后话：

每次这种题目我都是用的dfs，自己都烦了。来看看的牛逼方法吧。等着我在刷这题的时候尝试一下其他思路。