letterCombinations.txt

17. Letter Combinations of a Phone Number

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.
Return the answer in any order.

A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

class Solution {
public:
void DFS(string digits, int pos, string &path, vector<string> &res, vector<string> &letter){
            if(pos == digits.length()){
                res.push_back(path);
                return;
            }
            for(char c: letter[digits[pos] - '0']){
                path.push_back(c);
                DFS(digits,pos+1,path,res,letter);
                path.pop_back();
            }
        }
    vector<string> letterCombinations(string digits) {
        vector<string> res;
        if(digits.empty()) return res;
        vector<string> letter({"", "","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"});
        string path = "";
        DFS(digits,0,path,res,letter);
        return res;
    }
};