class Solution {
public:
    string reverseWords(string s) {
        int i = s.size()-1;
        string ans = "";
        
        while(i>=0){
            while(i>=0 && s[i] == ' ') i--;
            if(i<0){
                break;
            }
            int j = i;
            
            while(i>=0 && s[i] != ' ') i--;
            
           // cout << s.substr(i+1, j+1) << " i = " << i << ", j = " << j << endl;
            
            if(ans.empty()){
                ans.append(s.substr(i+1, j+1));
            }else{
                ans.append(" " + s.substr(i+1, j+1));
            }
        }
        
        return ans;
    }
};

Wrong Answer
Runtime: 0 ms
Your input
"the sky is blue"
Output
"blue is blue sky is  the"
Expected
"blue is sky the"