17. 电话号码的字母组合

Bertha 。 2022-09-08 14:48 202阅读 0赞

[https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number/][https_leetcode-cn.com_problems_letter-combinations-of-a-phone-number]

难度中等1465

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。答案可以按 **任意顺序** 返回。

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。

![ae1f9e931c60f753b50176ec16537070.png][]

**示例 1：**

输入：digits = "23"
    输出：["ad","ae","af","bd","be","bf","cd","ce","cf"]

**示例 2：**

输入：digits = ""
    输出：[]

**示例 3：**

输入：digits = "2"
    输出：["a","b","c"]

**提示：**

*  `0 <= digits.length <= 4`
 *  `digits[i]` 是范围 `['2', '9']` 的一个数字。

通过次数321,641提交次数562,718

class Solution {
            //装结果
            List<String> ans = new ArrayList<String>();
            //使用字符数组装字符实现对应
            String[] temp = {" ","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
            //                 0   1   2     3     4     5     6     7      8     9
    
        public List<String> letterCombinations(String digits) {
           if(digits.length()==0) return ans;
            dfs_find(digits, 0, "");      
            return ans;
        }
    
        void dfs_find(String digits,int n,String s)
        {
            if(digits.length() == n)
            {
                ans.add(s);
                return;
            }
    
            char c = digits.charAt(n);
            String c1 = temp[c-'0'];
            for(int i=0;i<c1.length();i++)
            {
                dfs_find(digits, n+1, s + c1.charAt(i));
            }
        }
    
    }

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_17_color_FFFFFF_t_70_g_se_x_16][]

[https_leetcode-cn.com_problems_letter-combinations-of-a-phone-number]: https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number/
[ae1f9e931c60f753b50176ec16537070.png]: /images/20220829/a5001b94dd6a4548a68ee47c3bb0989f.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_17_color_FFFFFF_t_70_g_se_x_16]: /images/20220829/d75409b1cd564dfc916bcc2751160a4d.png