String problems by using C++

151. Reverse Words in a String

My naive solution

class Solution {
public:
    string reverseWords(string s_) {
        if(s_.length()==0)return s_;
        vector<string> s;
        string this_c = "";
        for(auto c:s_)
        {
            if (c!=' ')
            {
                this_c += c;
            }
            else
            {
                s.push_back(this_c);
                this_c = "";
            }
        }
        s.push_back(this_c);
        reverse(s.begin(),s.end());
        string ret = "";
        for (auto word:s)
        {
            if (word=="")continue;
            ret += word;
            ret += " ";
        }
        if(ret.length()>0)ret.pop_back();
        return ret;
    }
};

A better solution from HERE by using Stringstream

class Solution {
public:
    string reverseWords(string s) {
        stringstream in(s);
        string word;
        string ret = "";
        while (in >> word) {
            reverse(word.begin(), word.end());
            ret += word + " ";
        }
        if (!ret.empty()) {
            ret.pop_back();
            reverse(ret.begin(), ret.end());
        }
        return ret;
    }
};