Remove $n$-th Node from End of List

https://leetcode.com/problems/remove-nth-node-from-end-of-list/

• Use prehead technique
• Instead of a stack, use two pointer to specify the window

prehead = ListNode(0)
prehead.next = head
first = second = prehead
for _ in range(n + 1):
    first = first.next
while first:
    first = first.next
    second = second.next
    second.next = second.next.next
return prehead.next