力扣-回溯-17 电话号码的字母组合

思路

和之前的回溯不同的是，要遍历完所有的数字，并且在单层递归逻辑里需要遍历一整个字符串

代码

class Solution {
public:
    vector<string> letters = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
    vector<string> result;
    string path;
    void backTracking(string dights, int curIndex){
        if(curIndex == dights.size()){
            result.push_back(path);
            return;
        }

        string letter = letters[(char)dights[curIndex] - '0'];
        for(int i = 0; i < letter.size(); i++){
            path.push_back(letter[i]);
            backTracking(dights, curIndex+1);
            path.pop_back();
        }
        return;
    }
    vector<string> letterCombinations(string digits) {
        if(digits == "") return result;
        backTracking(digits, 0);
        return result;
    }
};