LetterCombinationsPhone_Mul.cpp

class Solution {
private:
    vector<string> strDic = {"", "", "abc", "def", "ghi","jkl", "mno","pqrs", "tuv", "wxyz"};
    vector<string> finalVec;
public:
    vector<string> letterCombinations(string digits) {
        int len_d = digits.length();
       
        for(int i = 0; i < len_d; i++){
            int index = digits[i] - '0';
            finalVec = multiStr(finalVec, getList(strDic[index]));
        }
        return finalVec;
    }
    
    vector<string> getList(string &a){
        vector<string> ans;
        for(int i = 0; i< a.length(); i++){
            string temp = "";
            temp = temp + a[i];
            ans.push_back(temp);
        }
        return ans;
    }
    
    vector<string> multiStr(vector<string> &l1, vector<string> l2){
        if(l1.size() == 0 && l2.size() != 0){
            return l2;
        }
        if(l1.size() != 0 && l2.size() == 0){
            return l1;
        }
        vector<string> ans;
        for(int i = 0; i< l1.size(); i++){
            for(int j = 0; j < l2.size(); j++){
                ans.push_back(l1[i]+l2[j]);
            }
        }
        return ans;
    }
    
};