leetcode17-电话号码的字母组合

你的名字 2024-04-17 22:00 64阅读 0赞

*  [电话号码的字母组合][Link 1]
    
     *  [题目描述][Link 2]
     *  [code][]

# 电话号码的字母组合 #

## 题目描述 ##

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。

![image][]

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。

## code ##

package com.wangyg.leetcode;
    
    import org.junit.Test;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class LeetCode17 {
        @Test
        public void test() {
            Solution s = new Solution();
            System.out.println(s.letterCombinations("23").toString());
        }
    
        class Solution {
            public List<String> letterCombinations(String digits) {
                List<String> list = new ArrayList<>();
                String[] s = new String[digits.length()];
                if (s.length == 0) {
                    return list;
                }
                for (int i = 0; i < digits.length(); i++) {
                    switch (digits.charAt(i)) {
                        case '2':
                            s[i] = "abc";
                            break;
                        case '3':
                            s[i] = "def";
                            break;
                        case '4':
                            s[i] = "ghi";
                            break;
                        case '5':
                            s[i] = "jkl";
                            break;
                        case '6':
                            s[i] = "mno";
                            break;
                        case '7':
                            s[i] = "pqrs";
                            break;
                        case '8':
                            s[i] = "tuv";
                            break;
                        case '9':
                            s[i] = "wxyz";
                            break;
                    }
                }
                getAllTheStrings(s, 0, list, "");
                return list;
            }
            //获取所有的字符串
            private void getAllStrings(String[] str , int index, List<String> list, String tmp){
                if(index == str.length -1){
                    for(int i=0; i<str[index].length(); i++){
                        list.add(tmp+str[index].charAt(i));
                    }
                }
            }
    
            private void getAllTheStrings(String[] str, int index, List<String> list, String temp) {
                if (index == str.length - 1) { //这里是递归到最后一层时的逻辑
                    for (int i = 0; i < str[index].length(); i++) {
                        list.add(temp + str[index].charAt(i));
                    }
                } else { //这里是递归的逻辑
                    for (int i = 0; i < str[index].length(); i++) {  //循环+递归
                        getAllTheStrings(str, index + 1, list, temp + str[index].charAt(i));
                    }
                }
            }
        }
    }

[Link 1]: https://note.youdao.com/md/preview.html?file=%2Fyws%2Fapi%2Fpersonal%2Ffile%2F1891179F9B48400F8425136A0F4C8C1B%3Fmethod%3Ddownload%26read%3Dtrue%26shareKey%3D24ee5b1484411867100b9fd0fdccc103#%E7%94%B5%E8%AF%9D%E5%8F%B7%E7%A0%81%E7%9A%84%E5%AD%97%E6%AF%8D%E7%BB%84%E5%90%88
[Link 2]: https://note.youdao.com/md/preview.html?file=%2Fyws%2Fapi%2Fpersonal%2Ffile%2F1891179F9B48400F8425136A0F4C8C1B%3Fmethod%3Ddownload%26read%3Dtrue%26shareKey%3D24ee5b1484411867100b9fd0fdccc103#%E9%A2%98%E7%9B%AE%E6%8F%8F%E8%BF%B0
[code]: https://note.youdao.com/md/preview.html?file=%2Fyws%2Fapi%2Fpersonal%2Ffile%2F1891179F9B48400F8425136A0F4C8C1B%3Fmethod%3Ddownload%26read%3Dtrue%26shareKey%3D24ee5b1484411867100b9fd0fdccc103#code
[image]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9ub3RlLnlvdWRhby5jb20veXdzL3B1YmxpYy9yZXNvdXJjZS8yNGVlNWIxNDg0NDExODY3MTAwYjlmZDBmZGNjYzEwMy81NjVEMjZBNjI0NjM0MUM0QTUyMkNBNTAyMkI5N0I5Qz95bm90ZW1kdGltZXN0YW1wPTE1NjczNDc4MzYwNjA?x-oss-process=image/format,png