题目：

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

For example,

Given s = "the sky is blue",

return "blue is sky the".

Could you do it in-place without allocating extra space?

链接：  

6/21/2017

3ms, 39%

注意不要遗漏了最后一个reverse，end都是exclusive的，这样跟其他库函数类似。

1 public class Solution { 2     public void reverseWords(char[] s) { 3         if (s == null || s.length == 0) { 4             return; 5         } 6         reverse(s, 0, s.length); 7         int start = 0; 8         for (int i = 1; i < s.length; i++) { 9             if (s[i] == ' ') {10                 reverse(s, start, i);11                 start = i + 1;12             }13         }14         reverse(s, start, s.length);15         return;16     }17     private void reverse(char[] s, int start, int end) {18         for (int i = start, j = end - 1; i < j; i++, j--) {19             char tmp = s[i];20             s[i] = s[j];21             s[j] = tmp;22         }23         return;24     }25 }

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