题解 | #删除链表中重复的结点#

#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param pHead ListNode类 
# @return ListNode类
#
class Solution:
    def deleteDuplication(self , pHead: ListNode) -> ListNode:
        if not pHead:
            return pHead
        dummy = TreeNode(0)
        dummy.next = pHead
        pre = dummy
        cur = pre.next
        if cur:
            back = cur.next
        while back:
        	#如果不重复，向后平移三个指针
            if cur.val != back.val:
                pre = cur
                cur = back
                back = back.next
            else:
            	#如果出现重复，找到重复节点后边的第一个节点
                while back and cur.val == back.val:         
                    back = back.next
                #如果重复节点就是链表尾，直接删掉
                if not back:
                    pre.next = None
                    return dummy.next
                #删掉重复节点，更新cur和back
                pre.next = back
                cur = pre.next
                back = cur.next
        return dummy.next