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;
}