LeetCode - Refresh - Reverse Words in a String

class Solution {
public:
    void reverseWords(string &s) {
        string result;
        int len = s.size();
        for (int i = len-1; i >= 0; i--) {
            if (s[i] == ' ') {
                len = i;
            } else if (i == 0 || s[i-1] == ' ') {
                result += s.substr(i, len-i) + ' ';
            }
        }
        s = result.substr(0, result.size()-1);
    }
};