删除链表的倒数第N个节点-19

力扣（LeetCode） 链接：https://leetcode.cn/problems/remove-nth-node-from-end-of-list/discussion/

var removeNthFromEnd = function (head, n) {
  let dummy = new ListNode(null, head)
  let slow = dummy
  let fast = dummy
  for (let i = 0; i < n + 1; i++) {
    fast = fast.next
  }
  while (fast !== null) {
    slow = slow.next
    fast = fast.next
  }
  slow.next = slow.next.next
  return dummy.next
}