leetcode--Reverse Words in a String

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.

[java]  view plain  copy

1. public class Solution {  
2.     public String reverseWords(String s) {  
3.         Stack<Character> word = new Stack<Character>();  
4.         Stack<Character> sentence = new Stack<Character>();  
5.         char[] chars = s.toCharArray();  
6.         for(int i=0;i<=chars.length;i++){  
7.             if(i==chars.length||chars[i]==' '){  
8.                 if(!word.isEmpty()){  
9.                     if(!sentence.isEmpty()){  
10.                         sentence.add(' ');        
11.                     }  
12.                     while(!word.isEmpty()){  
13.                         sentence.add(word.pop());  
14.                     }                     
15.                 }                                                     
16.             }else{  
17.                 word.add(chars[i]);  
18.             }  
19.         }  
20.         StringBuilder sb = new StringBuilder();  
21.         while(!sentence.isEmpty()){  
22.             sb.append(sentence.pop());  
23.         }  
24.         return sb.toString();  
25.     }  
26. }  

原文链接http://blog.youkuaiyun.com/crazy__chen/article/details/46567103