Leetcode: Reverse Words in a String II

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?

这道题要求in-place做法，不能使用extra space, 那么，做法跟Rotate Array那道题非常相似

（1）reverse the whole array

（2）reverse each subarray seperated by ' '

 1 public class Solution {

 2     public void reverseWords(char[] s) {

 3         if (s.length == 0) return;

 4         reverse(s, 0, s.length-1);

 5         int last = 0;

 6         for (int i=0; i<s.length; i++) {

 7             if (s[i] == ' ') {

 8                 reverse(s, last, i-1);

 9                 last = i + 1;

10             }

11         }

12     }

13     

14     public void reverse(char[] s, int l, int r) {

15         while (l <= r) {

16             int temp = s[l];

17             s[l] = s[r];

18             s[r] = temp;

19             l++;

20             r--;

21         }

22     }

23 }