Reverse Words in a String

     void reverseWords(string &s) {
         string res = "", tmp = "";
         int l = s.length();
         int i = ;
         while(i < l){
             if(s[i] != ' ')
                 tmp += s[i++];
             else{
                 if(tmp != ""){
                     if(res == "")
                         res = tmp;
                     else{
                         res = tmp + " " + res;
                     }
                     tmp = "";
                 }
                 i++;
             }
         }
         if(res == "")
             res = tmp;
         else if(tmp != ""){
             res = tmp + " " + res;
         }
         s = res;
     }