leetcode-面试题-02.01-移除重复节点

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def removeDuplicateNodes(self, head: ListNode) -> ListNode:
        if not head:
            return head
        occurred = {head.val}
        pos = head
        # 枚举前驱节点
        while pos.next:
            # 当前待删除节点
            cur = pos.next
            if cur.val not in occurred:
                occurred.add(cur.val)
                pos = pos.next
            else:
                pos.next = pos.next.next
        return head