leetcode17
题目:
给定一个仅包含数字 2-9
的字符串,返回所有它能表示的字母组合。
给出数字到字母的映射如下(与电话按键相同)。注意 1 不对应任何字母。
示例:
输入:"23" 输出:["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
说明:
尽管上面的答案是按字典序排列的,但是你可以任意选择答案输出的顺序。
解题思路:
dfs递归
代码:
class Solution { public: vector<string> letterCombinations(string digits) { if (digits.empty()) return {}; vector<string> res; string dict[] = { "", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" }; letterCombinationsDFS(digits, dict, 0, "", res); return res; } void letterCombinationsDFS(string digits, string dict[], int level, string out, vector<string> &res) { if (level == digits.size()) { res.push_back(out); return; } string str = dict[digits[level] - '0']; for (int i = 0; i < str.size(); ++i) { letterCombinationsDFS(digits, dict, level + 1, out + string(1, str[i]), res); } } };