[Leetcode] 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.
Solution:
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 }