/*
 * [19] 删除链表的倒数第 N 个结点
 */

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function (head, n) {
  let dummy = new ListNode(0, head);

  let cur = dummy;
  let prev = dummy;
  let count = 0;

  while (cur.next) {
    if (count < n) {
      count++;
    } else {
      prev = prev.next;
    }
    cur = cur.next;
  }
  prev.next = prev.next.next;

  return dummy.next;
};