1105

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


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


typedef struct node Node;
typedef struct node * Link;


void create_newnode(Link *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("the link is emply!\n");
}


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


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


tmp = (*head)->next;


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


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


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


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


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


void release(Link *head)
{
Link tmp = NULL;


tmp = (*head)->next;


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


void revers_link(Link *head)
{
Link p1;
Link p2;
Link p3;


p3 = *head;


if(*head == NULL)
{
printf("the link is empty!\n");
return;
}
if(p3->next == NULL)
{
printf("this link has only one element!\n");
return;
}


p2 = p3->next;


if(p2->next == NULL)
{
p3->next = NULL;
*head =p2;
return;
}


p1 = p2->next;


while(p1->next != NULL)
{
p2->next = p3;
p3 = p2;
p2 = p1;
p1 = p1->next;
}
p2->next = p3;
p1->next = p2;
(*head)->next = NULL;
*head = 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_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);


// revers_link(&head);


release(&head);


display_node(head);
    return 0;
}