text: # coding:utf-8
  '''
  @Copyright:LintCode
  @Author:   lilsweetcaligula
  @Problem:  http://www.lintcode.com/problem/remove-duplicates-from-sorted-list
  @Language: Python
  @Datetime: 17-02-15 23:49
  '''
  
  """
  Definition of ListNode
  class ListNode(object):
      def __init__(self, val, next=None):
          self.val = val
          self.next = next
  """
  class Solution:
      """
      @param head: A ListNode
      @return: A ListNode
      """
      def deleteDuplicates(self, head):
          if head == None:
              return None
          
          slow = head
          fast = head.next
          
          while fast != None:
              if fast.val != slow.val:
                  slow.next = fast
                  slow      = slow.next
                  
              fast = fast.next
              
          slow.next = None
          
          return head