【LeetCode】017. Letter Combinations of a Phone Number

题目：

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"].

　　

题解：

Solution 1 ()

class Solution {

public:

    void dfs(string digits, int level, vector<string>& vv, string& s, vector<string> dict){

        if(level >= digits.size()) {

            vv.push_back(s);

            return;

        }

        string tmp = dict[digits[level] - ''];

        for(int i=; i<tmp.size(); ++i) {

            s.push_back(tmp[i]);

            dfs(digits, level+, vv, s, dict);

            s.pop_back();

        }

    }

    vector<string> letterCombinations(string digits) {

        if(digits.empty()) return vector<string>();

        vector<string> dict = {"abc","def","ghi","jkl",

                                "mno","pqrs","tuv","wxyz"};

        vector<string> vv;

        string s;

        dfs(digits, , vv, s, dict);

        return vv;

    }

};