链表中倒数第K个结点

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###题目

输入一个链表，输出该链表中倒数第k个结点。

###解题思路

快慢指针，快指针先走K。

###代码实现：

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# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def FindKthToTail(self, head, k):
        # 快慢指针，快指针先走
        if k == 0 or head is None:
            return None
        fast = head
        slow = head
        for i in range(0, k-1):
            fast = fast.next
            if fast is None:
                return None
        while fast.next is not None:
            fast = fast.next
            slow = slow.next
        return slow