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，做法跟那道题非常相似

（1）reverse the whole array

（2）reverse each subarray seperated by ' '

注意不要忘了reverse最后一个word

1 public void reverseWords(char[] s) { 2     // Three step to reverse 3     // 1, reverse the whole sentence 4     reverse(s, 0, s.length - 1); 5     // 2, reverse each word 6     int start = 0; 7     int end = -1; 8     for (int i = 0; i < s.length; i++) { 9         if (s[i] == ' ') {10             reverse(s, start, i - 1);11             start = i + 1;12         }13     }14     // 3, reverse the last word, if there is only one word this will solve the corner case15     reverse(s, start, s.length - 1);16 }17 18 public void reverse(char[] s, int start, int end) {19     while (start < end) {20         char temp = s[start];21         s[start] = s[end];22         s[end] = temp;23         start++;24         end--;25     }26 }