class Solution {

 public:

     /**

      * @param s A string

      * @return the length of last word

      */

     int lengthOfLastWord(string s) {

         int len = , tail = s.length() - ;

         while (tail >=  && s[tail] == ' ') tail--;

         while (tail >=  && s[tail] != ' ') {

             len++;

             tail--;

         }

         return len;

     }

 };