链表中倒数第k个节点

class Solution:
    def FindKthToTail(self, head, k):
        count = 0
        p = head
        while p:
            count += 1
            p = p.next
        if count < k:
            return None
        number = count-k+1
        new_count = 0
        pHead = head
        while pHead:
            new_count += 1
            if new_count == number:
                return pHead
            pHead = pHead.next