C++ 电话号码的字母组合

Posted 2021-09-28 L_add

电话号码的字母组合

题目描述

题目来源：力扣

string  num_str[10] = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
class Solution {
public:
   void _letterCombinations(const string& digits,int i,vector<string>& ret,string s)
    {
        if(i == digits.size())
        {
            ret.push_back(s);
            return ;
        }
        int num = digits[i] - '0';
        const string& l = num_str[num];
        for(auto ch : l)
        {
            _letterCombinations(digits,i+1,ret,s + ch);
        }
    }
    vector<string> letterCombinations(string digits) 
    {
        vector<string> ret;
        if(digits.empty())
        {
            return ret;
        }
            
        int i = 0;
        string s;
        _letterCombinations(digits,i,ret,s);
        return ret;
    }
};