151. Reverse Words in a String[medium]

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

For example,
Given s = "the sky is blue",
return "blue is sky the".

Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.

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.

一种思路是

• 
  class Solution {  
• public:  
•     void reverseWords(string &s) {  
•         istringstream is(s);  
•         s.clear();  
•         string tem;  
•         while(is >> tem)   
•             s = tem + " " + s;  
•         s = s.substr(0, s.size()-1);//因为尾部多了一个空格  
•     }  
• };  
  

  
  

  in-place in O(1) space: