Remove Nth Node From End of List

Description

Given a linked list, remove the n-th node from the end of list and return its head.

Example:

Given linked list: 1->2->3->4->5, and n = 2.
After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:

Given n will always be valid.

Follow up:

Could you do this in one pass?

Solution(javascript)

// 直觉上会想到利用链表的长度，事实上我们并不需要知道链表的长度
const removeNthFromEnd = (head, n) => {
  let h1 = head
  let h2 = null
  let count = 0
  while (h1) {
    count += 1
    h1 = h1.next
    if (h2) {
      h2 = h2.next
    }
    if (count === n + 1) {
      h2 = head
    }
  }
  if (!h2) {
    return head ? head.next : null
  }
  h2.next = h2.next.next
  return head
}