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[leetcode]Letter Combinations of a Phone Number

时间:2014-07-16 17:54:24      阅读:222      评论:0      收藏:0      [点我收藏+]

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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.

bubuko.com,布布扣

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.

 算法思路:

1.  很明显,这道题是组合问题combination,可以使用迭代来完成

2.  DFS。我的旧博客用的是combination的方法,不过当时心情不好,写的比较乱,这次我用的dfs,代码更简洁

 1 public class Solution {
 2 char[][] numberBoard = {{},{},{‘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‘}};
 3     public List<String> letterCombinations(String digits) {
 4         List<String> result = new ArrayList<String>();
 5         dfs(result,new StringBuilder(),digits);
 6         return result;
 7     }
 8     
 9     private void dfs(List<String> result,StringBuilder sb,String suffix){
10         if(suffix.length() == 0){
11             result.add(sb.toString());
12             return;
13         }
14         int index = suffix.charAt(0) - ‘0‘;
15         for(int i = 0; i < numberBoard[index].length; i++){
16             dfs(result, sb.append(numberBoard[index][i]), suffix.substring(1));
17             sb.deleteCharAt(sb.length() - 1);
18         }
19     }
20 }

 

 

 

 

[leetcode]Letter Combinations of a Phone Number,布布扣,bubuko.com

[leetcode]Letter Combinations of a Phone Number

标签:style   blog   http   color   使用   strong   

原文地址:http://www.cnblogs.com/huntfor/p/3847484.html

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