带头结点的循环单向链表

#include<stdio.h>
#include<stdlib.h>

struct node
{
	int num;
	struct node * next;
};

typedef struct node Node;
typedef struct node * Link;

void is_malloc_ok(Link new_node)
{
     if(new_node == NULL)
	{
		printf("malloc error!\n");
		exit(-1);
	}
}
void create_newnode(Link * new_node)
{
	*new_node = (Link) malloc(sizeof(Node));
	is_malloc_ok(*new_node);
}

void create_link(Link * head)
{
	create_newnode(head);
	(*head)->next = *head;
}

void insert_node_head(Link *head,Link new_node)
{
	new_node->next = (*head)->next;
	(*head)->next = new_node;
}

void display_node(Link head)
{
	Link tmp;
	tmp = head->next;
	if(tmp == head)
	{
		printf("Link is empty!\n");
		return;
	}

	while(tmp != head)
	{
		printf("num = %d\n",tmp->num);
		tmp = tmp->next;
	}
}



void insert_node_tail(Link *head,Link new_node)
{
    Link tmp;

	tmp = *head;

	while(tmp->next != *head)
	{
		tmp = tmp->next;
	}
	tmp->next = new_node;
	new_node->next = *head;

}

/*void insert_node_mid(Link *head,Link new_node,int num)
{
    Link tmp;
	tmp = *head;
    
	if(NULL == *head)
	{
		printf("link is empty!\n");
		return;
	}
	else
	{
    	while(tmp->num != num && tmp->next != NULL)
    	{
            tmp = tmp->next;
    	}
        if(tmp->num == num)
		{
            new_node->next = tmp->next;
			tmp->next = new_node;
		}
		else
		{
			printf("no such node!\n");
		}
	}

}*/

void delete_node(Link *head,int num)
{
	Link tmp;
	Link p;
	tmp = (*head)->next;
	p = *head;

	if(tmp == *head)
	{
		printf("link is empty!\n");
		return;
	}

	while(tmp->num != num && tmp->next != *head)
	{
		p = tmp;
		tmp = tmp->next;
	}

	if(tmp->num == num)
	{
		p->next = tmp->next;
		free(tmp);
	}
	else
	{
		printf("no such node!\n");
	}
}

void release(Link *head)
{
	Link tmp;

	tmp = (*head)->next;

	/*while (tmp != NULL)
	{
		*head = tmp->next;
		free(tmp);
		tmp = tmp->next;
	}*/
	while(tmp != *head)
	{
		(*head)->next = tmp->next;
		free(tmp);
		tmp = (*head)->next;
	}
}
void insert_node_mid(Link *head,Link new_node,int num)
{
	Link tmp;
	Link p;

	tmp = (*head)->next;
	p = *head;

	if(tmp == *head)
	{
		new_node->next = (*head)->next;
		(*head)->next = new_node;
		return;
	}
	else
	{
	while((num > tmp->num) &&(tmp->next != *head))
	{
		p = tmp;
		tmp = tmp->next;
	}
	if( tmp->next == *head)
	{
		if(num > tmp->num)
		{
			tmp->next = new_node;
			new_node->next = *head;
		}
		else
		{
			p->next = new_node;
			new_node->next = tmp;
		}
	}
	else
	{
		p->next = new_node;
		new_node->next = tmp;
	}
	}

}
void reverse_link(Link *head)
{
	Link p1 = NULL;
	Link p2 = NULL;
	Link p3 = NULL;

	if((*head)->next == *head ||(*head)->next->next == *head)
	{
		printf("No need reverse!\n");
		return;
	}
	else
	{
		p3 = (*head)->next;
		p2 = p3->next;
		if(p2->next == *head)
		{
			p2->next = p3;
			p3->next = *head;
			(*head)->next = p2;
			return;
		}
		p1 = p2->next;
		p3->next = *head;
		while(p1->next != *head)
		{
			p2->next = p3;
			p3 = p2;
			p2 = p1;
			p1= p1->next;
		}
		p2->next = p3;
		p1->next = p2;
		(*head)->next = p1;
	}
}

int main()
{
    Link head = NULL;
    Link new_node = NULL;
    int i;
	int num;

	create_link(&head);

	for(i = 0; i < 10;i++)
	{
        create_newnode(&new_node);
		new_node->num = i;
		//insert_node_mid(&head,new_node,new_node->num);
		insert_node_head(&head,new_node);
		//insert_node_tail(&head,new_node);
	}

	printf("please input a num!\n");
	scanf("%d",&num);

	//create_newnode(&new_node);
	//new_node->num =  num;
	
	//insert_node_mid(&head,new_node,num);
	delete_node(&head,num);
    
	display_node(head);

    release(&head);

    //reverse_link(&head);

	display_node(head);

    return 0;
}