Remove Nth Node From End of List (in one pass)

LeetCode_RemoveNthNodeFromEndList.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def removeNthFromEnd(self, head, k):
        """
        :type head: ListNode
        :type k: int
        :rtype: ListNode
        """
        to_return, future = head, head
        for _ in range(k):
            future = future.next
        
        prev = None
        while future is not None:
            prev = head
            head = head.next
            future = future.next
        
        if prev is None:
            return head.next
        else:
            prev.next = head.next
            del head
            return to_return