[Leetcode] Letter Combinations of a Phone Number

 1 public class Solution {
 2     public List<String> letterCombinations(String digits) {
 3         String[] maps={""," ","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
 4         List<String> result = new ArrayList<String>();
 5         dfs(result, maps, digits,0,"");
 6         return result;
 7     }
 8 
 9     private void dfs(List<String> result, String[] maps, String digits, int level, String temp) {
10         // TODO Auto-generated method stub
11         if(level>digits.length())
12             return;
13         if(digits.length()==level){
14             result.add(temp);
15             return;
16         }
17         int curDig=digits.charAt(level)-48;
18         for(int i=0;i<maps[curDig].length();++i){    //此时从0开始到maps[curDig]结束，为temp里可以加的字母的取值范围
19             temp+=maps[curDig].charAt(i);
20             dfs(result, maps, digits, level+1, temp);
21             temp=temp.substring(0, temp.length()-1);
22         }    
23     }
24 }