https://leetcode.cn/problems/remove-nth-node-from-end-of-list/submissions/ (opens new window) 标签 需要注意的点

1. 虚拟节点指向head
2. 边界问题

class Solution:
    def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:

        dummyNode = ListNode(-1)
        dummyNode.next = head
        xNode = self.findNodeX(dummyNode, n+1)
        xNode.next = xNode.next.next
        return dummyNode.next
    

    def findNodeX(self, node, k):
        p1 = node
        # p1 先走k
        for i in range(k):
            p1 = p1.next
        
        p2 = node

        # 同时走n-k
        while p1:
            p1 = p1.next
            p2 = p2.next
        
        return p2