实现链表逆序（头插）

#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_new_node(Link *new_node)

{
(*new_node)=(Link)malloc(sizeof(Node));
is_malloc_ok(*new_node);

}//建立表头结点

void create_link(Link * head)

{
create_new_node(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;

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

}

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 = NULL;
tmp=(*head);

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

}

void insert_node_mid(Link *head,Link new_node,int num)

{
Link p1 = NULL;
Link p2 = NULL; 
p1 = *head;

    p2 = p1->next;
if(NULL == p2)
{
printf("link is empty!\n");
return;
}
else
{

    while(p2->num != num && p2->next != NULL)

    {

            p2 = p2->next;

    }

        if(p2->num == num)
{

            new_node->next = p2->next;
p2->next = new_node;
}
else
{
printf("no such node!\n");
}
}

}

void revers_link(Link *head)//链表倒序

{

    Link p3 = *head;
Link p2 = p3->next;
Link p1 = p2->next;

if(*head==NULL)
{
return;
}//链表为空时
if(p3->next=NULL)
{
   return;
}//链表中只含1个节点
if( p2->next==NULL)
{
p2 = p3->next;
*head = p2;
p3->next=NULL;
}//链表只含2个结点
while(p1->next!= NULL)
{
   p2->next = p3;
p3 = p2;
p2 = p1;
p1 = p1->next;
}
p2->next=p3;
p1->next=p2;
*head = p1;

}

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_node(Link *head)

{
Link p;
p=(*head)->next;
if (p == NULL)
{
printf("link is empty!\n");
return;
}
while(*head != p)
{
(*head)->next=p->next;
free(p);
p=(*head)->next;
}

}

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);

// display_node(head);

  release_node(&head);//释放链表

display_node(head);//显示链表

    return 0;

}