19. Remove Nth Node From End of List

class Solution:
    def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
        p = q = head
        while n:
            q = q.next
            n-=1
        if not q:  #to remove head node (q will go beyond length of list)
            return head.next
        while q.next:
            p = p.next
            q = q.next

        p.next = p.next.next
        return head