Leetcode:Letter Combinations of a Phone Number 手机键盘字母映射

Letter Combinations of a Phone Number：

Given a digit string, return all possible letter combinations that the number could represent.



A mapping of digit to letters (just like on the telephone buttons) is given below.

 

Input:Digit string "23"

Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

 

解题分析：

暴力深搜

使用vector<string>模拟一个映射 比使用 map要方便

class Solution {

public:

    vector<string> letterCombinations(string digits) {

        const vector<string> letter = {" ", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}; // 0,1,2...

        vector<string> result;

        dfs(letter, digits, 0, "", result);

        return result;

        

    }

    

    void dfs(const vector<string>& letter, string& digits, int cur, string path, vector<string>& result) {

        if (cur == digits.size()) {

            result.push_back(path); return;

        }

        for (auto c : letter.at(digits.at(cur) - '0')) {

            dfs(letter, digits, cur + 1, path + c, result);

        }

    }

};