Leetcode 17. 电话号码的字母组合

Leetcode 17. 电话号码的字母组合

class Solution {
    string numToStr[10] = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
public:
    void letterCombinationsChild(string digits, size_t i, string combine, vector<string>& vecV)
    {
        if(i == digits.size())
        {
            vecV.push_back(combine);
            return;
        }

        // "234"
        int num = digits[i] - '0';
        string str = numToStr[num];
        for(char ch : str)
        {
            combine += ch;
            letterCombinationsChild(digits,i+1,combine,vecV);
            combine.pop_back();
        }
    }

    vector<string> letterCombinations(string digits) {
        vector<string> vecV;
        if(digits.empty())
        {
            return vecV;
        }
        string combine;
        int i = 0;
        letterCombinationsChild(digits,i,combine,vecV);
        return vecV;
    }
};