stringstream 简单应用

class Solution {
public:
    string reverseWords(string s) {
        stack<string> stk;
        string res = "";
        stringstream ss;
        ss << s;
        string input;
        while(ss >> input){
            stk.push(input);
        }
        while(!stk.empty()){
            res += stk.top();
            stk.pop();
            if(!stk.empty())res += " ";
        }

        return res;
    }
};