leetcode-Reverse Words in a String

class Solution {
public:
    void reverseWords(string &s) {
        deque<string> ds;
        int b, i(0), len(s.size());
        while (i < len) {
            while (i<len && s[i]==' ') ++i;
            if (i == len) break;
            b = i;
            while (i<len && s[i]!=' ') ++i;
            ds.push_front(s.substr(b, i-b));
        }
        s = "";
        if (ds.empty()) return;
        s += ds[0];
        for (i=1; i<ds.size(); ++i) s += " " + ds[i];
        
    }
};

class Solution:
    # @param s, a string
    # @return a string
    def reverseWords(self, s):
        ss = s.split()
        ss.reverse()
        return " ".join(ss)