19 - 删除链表的倒数第 N 个结点 about leetcode HOT 1 OPEN

class ListNode {
  val: number;
  next: ListNode | null;
  constructor(val?: number, next?: ListNode | null) {
    this.val = val === undefined ? 0 : val;
    this.next = next === undefined ? null : next;
  }
}
function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
  let dummy: any = new ListNode(0, head);
  let left = dummy;
  let right = dummy;
  while (n >= 0) {
    right = right.next;
    n--;
  }
  while (right) {
    right = right.next;
    left = left.next;
  }
  left.next = left.next.next;
  return dummy.next;
}

const l1 = new ListNode(1);
l1.next = new ListNode(2);
l1.next.next = new ListNode(3);
l1.next.next.next = new ListNode(4);

console.log(removeNthFromEnd(l1, 3));