题解 | 链表中倒数最后k个结点

class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution:
    def FindKthToTail(self , pHead: ListNode, k: int) -> ListNode:
        first = pHead
        second = pHead
        n = 0
        while n < k and first:
            first = first.next
            n += 1

        if first is None and n < k:
            return None

        while first:
            second = second.next
            first = first.next
        return second