Question: Reverse Words in a String
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.
思路：每个单词按顺序翻转，组合每个单词，对组合的句子再翻转。
例子： s = "ab cd"
<1>s的单词翻转后是"ba dc",记为_s
<2>将_s再翻转后是"cd ab"