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// @Title: 删除链表的倒数第 n 个结点 (删除链表的倒数第 n 个结点)
// @Author: 15816537946@163.com
// @Date: 2022-03-26 16:05:54
// @Runtime: 0 ms
// @Memory: 2.1 MB
/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */

func removeNthFromEnd(head *ListNode, n int) *ListNode {
	if head == nil {
		return head
	}

	cursor := new(ListNode)
	cursor.Next = head
	slow, fast := cursor, cursor

	for i := 0; i <= n; i++ {
		fast = fast.Next
	}

	for fast != nil {
		fast = fast.Next
		slow = slow.Next
	}
	slow.Next = slow.Next.Next

	return cursor.Next
}