LeetCode:Reverse Words in a String

 1 class Solution {
 2 public:
 3     void reverseWords(string &s) 
 4     {
 5         //从前往后扫描 
 6         string res, word;
 7         for(int i = s.size()-1; i >= 0;)
 8         {
 9             while(i >= 0 && s[i] == ' ')--i;//去掉空格
10             if(i < 0)break;
11             if(res.size() != 0)res.push_back(' ');
12             word.clear();
13             while(i >= 0 && s[i] != ' ')word.push_back(s[i--]);//word为找到的一个单词
14             for(int j = word.size()-1; j >= 0; --j)
15                 res.push_back(word[j]);
16         }
17         s = res;
18     }
19 };