先整体翻转，再对每个单词翻转

C++ 代码

class Solution {
public:
    string reverseWords(string s) {
        reverse(s.begin(), s.end());
        int cur = 0;
        for(int i = 0; i < s.size(); ++ i){
            if(s[i] == ' '){
                reverse(s.begin() + cur, s.begin() + i);
                cur = i + 1;
            }
        }
        reverse(s.begin() + cur, s.end());
        return s;
    }
};