Leetcode:letter combinations of a phone number keypad letter Map

Letter combinations of a Phone number:

Given a digit string, return all possible letter combinations, the number could represent.

A mapping of Digit to letters (just as on the telephone buttons) is given below.

Input:digitstring " at"Output: ["AD","AE","af","BD"," be","BF","CD","CE","CF"].

Problem Solving Analysis:

Deep search of violence

Using vector<string> to simulate a map is easier than using a map

classSolution { Public: Vector<string> Lettercombinations (stringdigits) {        Constvector<string> letter = {" ","","ABC","def","Ghi","JKL","MnO","PQRS","TUV","WXYZ"};//0,1,2 ...vector<string>result; DFS (letter, digits,0,"", result); returnresult; }        voidDfsConstvector<string>& Letter,string& Digits,intCurstring Path, vector<string>&result) {        if(cur = =digits.size ())            { result.push_back (path); return; }         for(Auto c:letter.at (digits.at (cur)-'0') {DFS (letter, digits, cur+1,path + c, result); }    }};