双向循环链表函数（有删除，增加，排序，统计等功能）

#include<stdio.h>

#include<stdlib.h>

struct node

{

    int num;

    char name[20];

    struct node *next;

    struct node *prior;

};

typedef struct node Node;

typedef struct node *Link;

void is_malloc_ok(Link new_node)

{

    if (new_node == NULL)

        exit(-1);

}

void create_new_node(Link *new_node)

{

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

  

    is_malloc_ok(*new_node);

}

void create_bilateral_cycle(Link *head)  //带表头的双向循环链表，链表中只有表头，表头的前驱和后继都是本身

{

    create_new_node (head);

    (*head)->prior = *head;

    (*head)->next = *head;

}

void insert_node_head(Link head, Link new_node)  // 头插，每一次插入把结点作为表头的直接后继，

{

    Link p;

    p = head;

    new_node->prior = p;

    new_node->next = p->next;

    p->next->prior = new_node;

    p->next = new_node;

   

}

void insert_node_tail(Link head, Link new_node)  //尾插，每一次插入把结点作为表头的直接前驱

{

    Link p;

    p = head;

    new_node->prior = p->prior;

    new_node->next = p;

    p->prior->next = new_node;

    p->prior = new_node;

}

void display_forward (Link head)  //输出函数：从表头的直接后继开始输出

{

    Link p;

    p = head->next;

    if (p == head)

    {

        printf("The link is empty!");

        return;

    }

    while (p != head)

    {

        printf("%4d: %s\n",p->num,p->name);

 p = p->next;

    }

}

 

void display_backward (Link head)  //输出函数:从表头的直接前驱开始输出

{

    Link p;

    p = head->prior;

    if (p == head)

    {

        printf("The link is empty!");

 return;

    }

    while (p != head)

    {

        printf("%4d: %s\n",p->num,p->name);

        p = p->prior;

    }

}

int count (Link head)   //计数函数：计算除了表头外所有的结点数

{

    int n = 0;

    Link p;

    p = head->next;

   

    while ( p != head)

    {

        n++;

 p = p->next;

    }

    return n;

}

Link search (Link head, int n)  //搜索函数：输入结点中成员num的值，返回成员所在结点的地址

{

    Link p;

    p = head->next;

 

    while ( p != head )

    {

        if (p->num == n)

        {

     break;

 }

 p = p->next;

    }

    return p;

}

void delete_node (Link head, int n) //删除函数：输入结点中num的值，删除成员所在结点

{

    Link p;

    p = search (head,n);

   

    if (p == head)

    {

        printf("没有这个值！");

 return;

    }

   

    p->next->prior = p->prior;

    p->prior->next = p->next;

    free(p);

   

}

void insert_sort(Link head, Link new_node)  //边排边插函数，将结点有序的插在链表中

{

    Link p;

    p = head->prior;

    int number = new_node->num;

   

    if (p == head)

    {

        head->next = new_node;

 head->prior = new_node;

 new_node->next = head;

 new_node->prior = head;

    }

    else if (number <= p->num)

    {

 new_node->next = head;

 new_node->prior = head->prior;

 head->prior->next = new_node;

        head->prior = new_node;

    }

    else if (number >= head->next->num)

    {

        new_node->prior = head;

 new_node->next = head->next;

 head->next->prior = new_node;

        head->next = new_node;   

    }

    else

    {

        while ( p != head)

        {

     if (number <= p->num)

     {

         new_node->prior = p;

  new_node->next = p->next;

  p->next->prior = new_node;

  p->next = new_node;

  break;

     }

     p = p->prior;

 }

    }

}

void plus_node(Link head, int n)   //增加结点函数：输入成员中num的值，将结点放在该成员所在结点的前面

{

    Link new_node;

    Link p;

    p = search(head,n);

   

    create_new_node(&new_node);

  

   if (p = head)

    {

        printf("Fail!");

 return ;

    }

  

    printf("输入新结点的num值");

    scanf("%d",&new_node->num);

    printf("输入新结点的name值");

    scanf("%s",new_node->name);

    new_node->next = p;

    new_node->prior = p->prior;

    p->prior->next = new_node;

    p->prior = new_node;

}

void release (Link *head)    //释放函数：释放所有的空间

{

    Link p;

    p = (*head)->prior;

   

    if (p == *head)

    {

        free(p);

 return;

    }

    while (p != *head)

    {

       (*head)->prior = p->prior;

        p->prior->next = *head;

 free(p);

 p = (*head)->prior;

    }

}

int main()

{

    Link head = NULL;

    Link new_node = NULL;

    int i;

    int n;

    create_bilateral_cycle(&head);

   

    for(i = 1; i < 3; i++)

    {

        create_new_node(&new_node);

       

 new_node->num = i;

 printf("输入第%d个人的名字",i);

        scanf("%s",new_node->name);

       insert_node_head(head,new_node);

// insert_node_tail(head,new_node);

    }

   

    display_forward(head);

    printf("此链表有%d个结点。",count(head));

    printf("输入结点中num值，删除此结点：");

    scanf("%d",&n);

    delete_node (head,n);

    display_forward(head);

    printf("输入结点中num值，在前面加一个结点：");

    scanf("%d",&n);

    plus_node(head,n);

    display_forward(head);

    for (i = 1; i < 3; i++)

    {

        create_new_node(&new_node);

        printf("输入插入的第%d个结点的值：",i);

 scanf("%d",&new_node->num);

        printf("输入插入的第%d个结点的名字：",i);

 scanf("%s",new_node->name);

 insert_sort(head,new_node);

    }

    display_backward(head);

   

    release(&head);

    display_backward(head);

    return 0;

}