Title: 1-1-2-3-3-3-4-5-6-6-7, delete duplicate node returned 2-4-5-7
def delete_duplicate(head): h = Node(0) k = h p = head if not p or not p.next: return head q = p.next if p.val!=q.val: k.next = p k = k.next while q.next: if q.val!=p.val and q.val!=q.next.val: k.next = q k = k.next p = q q = q.next if p.val!=q.val: k.next = q k = k.next k.next = None return h.next
Note: The criteria for the node will not be repeated, and before and after the node is not the same, attention head node and tail node to be determined separately.