C语言 双向循环链表带表头结点（2018.12.22）

双向循环链表带表头结点
创建+头插+尾插+中间插入+删除+反序+释放内存

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

#define MAL_OK 1
#define MAL_ERR 0

struct dnode
{
    int num;
    struct dnode *next,*prior;
};

typedef struct dnode Dnode;
typedef struct dnode * Dlink;

int malloc_ok(Dlink new_node)
{
    if(new_node == NULL)
    {
        return MAL_ERR;
    }
    else
    {
        return MAL_OK;
    }
}

void create_node(Dlink * new_node,int i)
{
    (*new_node) = (Dlink)malloc(sizeof(Dnode));
    while(malloc_ok(*new_node) == MAL_ERR)
    {
        (*new_node) = (Dlink)malloc(sizeof(Dnode));
    }
    (*new_node)->num = i;
}

void create_link(Dlink * head)
{
    create_node(head,0);
    (*head)->prior = *head;
    (*head)->next = *head;
}

void insert_node_head(Dlink head,Dlink new_node)
{
    if(head->next == head)
    {
        head->prior = new_node;
    }
    else
    {
        head->next->prior = new_node;
    }
    new_node->next = head->next;
    new_node->prior = head;
    head->next = new_node;

}

void insert_node_tail(Dlink head,Dlink new_node)
{
    Dlink p;
    p = head;
    while(p->next != head)
    {
        p = p->next;
    }
    p->next = new_node;
    new_node->next = head;
    new_node->prior = p;
    head->prior = new_node;
}

void insert_node_mid(Dlink head,Dlink new_node,int num_loc)
{
    Dlink p;
    p = head->next;

    while(p->num != num_loc && p->next != head)
    {
        p = p->next;
    }
    if(p->next == head && p->num !=num_loc)
    {
        p->next = new_node;
        new_node->next = head;
        new_node->prior = p;
        head->prior = new_node;
    }
    else
    {
        p->prior->next = new_node;
        new_node->prior = p->prior;
        new_node->next = p;
        p->prior = new_node;
    }

}

void del_node(Dlink head,int num_val)
{
    Dlink p;
    p = head->next;

    if(p == head)
    {
        printf("Link is empty._2\n");
    }
    else
    {
        while(p->num != num_val && p->next != head)
        {
            p = p->next;
        }
        if(p->next == head && p->num != num_val)
        {
            printf("没有找到数。\n");
        }
        else
        {
            p->prior->next = p->next;
            p->next->prior = p->prior;
            free(p);
        }
    }
}

void release_link(Dlink * head)
{
    Dlink p;
    p = (*head)->next;

    if(p == *head)
    {
        printf("Link is empty._3\n");
        free(p);
        *head = NULL;
    }
    else
    {
        while(p != *head)
        {
            (*head)->next = p->next;
            free(p);
            p = (*head)->next;
        }
        free(*head);
        *head = NULL;
    }
}

void display(Dlink head)
{
    Dlink p;
    p = head;

    if(p == NULL)
    {
        printf("No Link.\n");
    }
    else if(p->next == head)
    {
        printf("Link is empty._1\n");
    }
    else
    {
        while(p->next != head)
        {
            p = p->next;
            printf("num = %d\n",p->num);
        }
    }
}

void display2(Dlink head)
{
    Dlink p;
    p = head;

    if(p == NULL)
    {
        printf("No Link.\n");
    }
    else if(p->next == head)
    {
        printf("Link is empty.\n");
    }
    else
    {
        while(p->prior != head)
        {
            p = p->prior;
            printf("num = %d\n",p->num);
        }
    }
}

int main()
{
    Dlink head;
    Dlink new_node;
    int i;
    int num_val,num_loc;

    create_link(&head);
    for(i = 0;i < 10; i++)
    {
        create_node(&new_node,i);
        insert_node_tail(head,new_node);
    }

    display(head);
    
    printf("请输入要插入的位置。\n");
    scanf("%d",&num_loc);
    printf("请输入要插入的数。\n");
    scanf("%d",&num_val);
    create_node(&new_node,num_val);
    insert_node_mid(head,new_node,num_loc);
    display(head);
    
    printf("请输入要删除的数。\n");
    scanf("%d",&num_val);
    del_node(head,num_val);
    display(head);

    printf("********************\n");
    display2(head);

    release_link(&head);
    display(head);
    return 0;
}