186. Reverse Words in a String II

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

Example:

Input:  

["t","h","e"," ","s","k","y"," ","i","s"," ","b","l","u","e"]
Output: 

["b","l","u","e"," ","i","s"," ","s","k","y"," ","t","h","e"]

Note: 

• A word is defined as a sequence of non-space characters.
• The input string does not contain leading or trailing spaces.
• The words are always separated by a single space.

Follow up:  Could you do it in-place without allocating extra space