12.29

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


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


typedef struct node Node;
typedef struct node * Link;


void create_link(Link * head)
{
*head = NULL;
}


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


void display_node(Link head)
{
Link tmp;
tmp = head;


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


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)/*灏炬彃*/
{
    Link tmp;


tmp = *head;


if(*head == NULL)
{
*head = new_node;
new_node->next = *head;
}
else 
{
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)/*涓棿鎻?/
{
    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)/*鍒犻櫎缁撶偣*/
{
Link tmp;
Link p;
tmp = p = *head;


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


while(tmp->num != num && tmp->next != *head)
{
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(Link *head) /*閲婃斁鎵€鏈夌粨鐐?/
{
    Link tmp;
Link head_old;
head_old=*head;
tmp=*head;
if(*head==NULL)
{
printf("link is empty!\n");
return;
}
while(tmp->next!=head_old)
{
*head=(*head)->next;
free(tmp);
tmp=(*head);
}
free(tmp);
*head=NULL;
}


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,10);
    
//delete_node(&head,num);
//release_link(&head);/*閲婃斁鎵€鏈夌粨鐐?/


display_node(head);

    return 0;
}