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

class Solution:
    def getKthFromEnd(self, head: ListNode, k: int) -> ListNode:
        first, cur, lens =head, head, 0
        while first:
            first = first.next
            lens += 1
        for i in range(lens-k):
            cur = cur.next
        return cur

class Solution:
    def getKthFromEnd(self, head: ListNode, k: int) -> ListNode:
        fast, slow = head, head
        for _ in range(k):
            if not fast:
                return
            fast = fast.next
        while fast:
            fast, slow = fast.next, slow.next
        return slow