输入一个单向链表，输出该链表中倒数第k个结点。链表的倒数第0个结点为链表的尾指针
typedef struct _node_t
{struct _node_t *next;int data;
}Node;Node *list_k_node(Node * head, int k)
{Node *p=head, *pk=head;if (NULL == head || (0 >= k)){return NULL;}for (; k > 0; k--) ///K > 0{if (pk->next!=NULL) pk = pk->next;else return NULL;}while (pk->next!=NULL) {p=p->next;pk=pk->next;}return p;
}
)
)
)
