leetcode17(letter-combinations-of-a-phone-number)

class Solution {
    
public:vector<string> letterCombinations(string digits) {
    if(digits=="") return vector<string>();//用数组存储号码键对应的字符串,下标代表号码键的数字string res[10] = {
    "","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};vector<string> arr;digui("",digits,res,0,arr);return arr;}void digui(string key,string digits,string res[10],int index,vector<string>& arr){
    int k = digits[index]-'0';//获取输入字符串内部的字符,记得转一下类型if(key.size()==digits.size()){
    arr.push_back(key);return;}for(int i=0;i<res[k].size();++i){
    //递归+回溯key.push_back(res[k][i]);digui(key,digits,res,index+1,arr);key.pop_back();}}
};