1. Reverse Words in a String

1. 题目

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

For example,

Given s = "the sky is blue",

return "blue is sky the".
Clarification:

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

2. source code