数据结构（八）双向循环链表

定义结构体

typedef struct node
{
    DataType value;
    struct node *next; //保存前一个结点的地址
    struct node *front;//保存后一个结点的地址
 
}doublelist;

//创建一个空的双向循环链表

doublelist * DoublelistCreate()
{
    doublelist *head = (doublelist *)malloc(sizeof(doublelist));
    head->next = head;
    head->front = head;
    return head;
}

//插入数据

void DoublelistInsert(doublelist *head, DataType value)
{
    doublelist *tmp = (doublelist *)malloc(sizeof(doublelist));
    tmp->value = value;
    
    tmp->next = head->next; 
    tmp->front = head;
    head->next->front = tmp;
    head->next = tmp;
}

//遍历链表
void DoublelistPrint(doublelist *head)
{
    doublelist *tmp = head;
    while(tmp->next != head)
    {
        tmp = tmp->next;
        printf("%d  ", tmp->value);       
    }
    putchar('\n');
}

//头删法
DataType DoublelistDeleteHead(doublelist *head)
{
    if(head->next == head)
    {
        printf("链表为空");
        return -1;
    }
    doublelist *tmp = head->next;
    DataType value = tmp->value;
    head->next = tmp->next;
    tmp->next->front = head;
 
    free(tmp);
    tmp = NULL;
 
    return value;
}