new_contents: class Solution:
      # @param {string} s
      # @return {string}
  
      def shortestPalindrome(self, s):
          r = s[::-1]
          for i in xrange(len(s)+1):
              if s.startswith(r[i:]):
                  return r[:i] + s
  
subject: add solution for Shortest Palindrome