Leetcode刷题笔记题解（C++）：17. 电话号码的字母组合

 

思路：回溯方法来解决

class Solution {
public:
    map M={{'2',"abc"},{'3',"def"},{'4',"ghi"},{'5',"jkl"},{'6',"mno"},{'7',"pqrs"},{'8',"tuv"},{'9',"wxyz"}};
    vector letterCombinations(string digits) {
        vector res;
        string temp;
        if(digits.size()==0) return res;
        Dfs(0,digits,res,temp);
        return res;
    }
    void Dfs(int index,string digits,vector &res,string temp){
        if(temp.size()==digits.size()){
            res.push_back(temp);
            return;
        }
        for(int i=0;i