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
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param pHead ListNode类 
# @param k int整型 
# @return ListNode类
#
class Solution:
    def FindKthToTail(self , pHead: ListNode, k: int) -> ListNode:
        # write code here
        if not pHead or k <= 0:
            return None
        slow = pHead
        fast = pHead

        for _ in range(k):
            if not fast:
                return None
            fast = fast.next

        while fast:
            slow = slow.next
            fast = fast.next

        return slow