【leetcode刷题笔记】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"].

Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.

代码如下：

 1 public class Solution {
 2     public List<String> letterCombinations(String digits) {
 3         ArrayList<String> answer = new ArrayList<String>();
 4
 5         char[][] map = {{‘a‘,‘b‘,‘c‘},{‘d‘,‘e‘,‘f‘},{‘g‘,‘h‘,‘i‘},{‘j‘,‘k‘,‘l‘},{‘m‘,‘n‘,‘o‘},{‘p‘,‘q‘,‘r‘,‘s‘},{‘t‘,‘u‘,‘v‘},{‘w‘,‘x‘,‘y‘,‘z‘}};
 6         String currentPath = new String();
 7
 8         DeepSearch(map, answer, digits, currentPath);
 9         return answer;
10     }
11
12     public void DeepSearch(char[][] map,List<String> answer,String digits,String currentPath){
13         if(digits.length() == 0)
14         {
15             String temp = new String(currentPath);
16             answer.add(temp);
17
18             return;
19         }
20
21         int now = digits.charAt(0) - ‘0‘;
22         for(int j = 0;j < map[now-2].length;j++){
23             currentPath += map[now-2][j];
24             DeepSearch(map, answer, digits.substring(1), currentPath);
25             currentPath = currentPath.substring(0, currentPath.length()-1);
26         }
27     }
28 }

【leetcode刷题笔记】Letter Combinations of a Phone Number