嵌入式 Linux C语言（十三）——双链表

嵌入式 Linux C语言（十三）——双链表

一、双链表简介

1、双链表的结构

双链表是链表的一种，由节点组成，每个数据结点中都有两个指针，分别指向直接后继和直接前驱。

2、双链表的节点

typedef struct data
{
unsigned int id;//学生身份ID
char name[LENGTH];//学生姓名
char subject[LENGTH];//科目
unsigned int score;//分数
}DATA,*PDATA;

typedef struct node
{
struct node *prev;
unsigned int num;//节点序号，头节点则保存链表的节点数量
DATA data;//数据
struct node *next;
}Node,*DList;




二、双链表的操作

1、双链表的创建

双链表头结点的创建：
DList dlist_init(void)
{
DList head = (Node *)malloc(sizeof(Node));
if(NULL == head)
{
fprintf(stderr, "dlist_init function malloc failure.\n");
return NULL;

}
head->next = NULL;
head->prev = NULL;
return head;
}
采用尾部插入节点的方式创建双链表int dlist_create(DList head, unsigned int num)
{
DList p,r;
r = head;
int i;
for(i = 0; i < num; i++)
{
p = (Node *)malloc(sizeof(Node));//创建新节点
if(NULL == p)
{
fprintf(stderr, "dlist_create function p malloc failed.\n");
return ERROR;
}
p->num = i+1;//将各个节点的序号写入节点成员num
p->data.id = 1000 + i;
strcpy(p->data.name, "scorpio");
strcpy(p->data.subject, "English");
p->data.score = 100;
r->next = p;
p->prev = r;
r = p;
}
r->next = NULL;
head->num = dlist_size(head);//将创建链表的大小写入头结点num成员
return OK;
}

2、双链表的销毁

void dlist_destroy(DList list)
{
DList p;
while(list)
{
p = list->next;
free(list);
list = p;
}
}

3、双链表的节点插入操作

void dlist_insert(DList list, unsigned int i, PDATA data)
{
if(dlist_size(list) < i)
{
fprintf(stdout, "dlist_insert function failed.The list size is too samll.There is no element %u.\n", i);
return ;
}
//创建一个节点
DList p = (Node *)malloc(sizeof(Node));
//利用传入的data结构体的数据对节点的数据域进行初始化
p->data.id = data->id;
strcpy(p->data.name, data->name);
strcpy(p->data.subject, data->subject);
p->data.score = data->score;
//找到节点i
DList r = list->next;
if(NULL == r->next)//链表为空时，直接插入
{
//插入节点到链表
p->next = r->next;
r->next = p;
p->prev = r;
}
else//链表不为空时，先查找插入的位置
{
while(i != r->num)
{
r = r->next;
}
//插入节点到链表
p->next = r->next;
r->next = p;
p->prev = r;
}
//顺延链表节点i后的节点的序号
int n = i + 1;
r = r->next;
while(r->next)
{
r->num = n++;
r = r->next;
}
r->num = n;//尾节点的序号
list->num = dlist_size(list);//将链表的大小写入头结点num成员
}

4、双链表的节点的删除操作

void dlist_delete(DList list, unsigned int i)
{
if(dlist_size(list) < i)
{
fprintf(stdout, "dlist_insert function failed.The list size is too samll.There is no element %u.\n", i);
return ;
}
DList r = list->next;
//查找要删除节点的位置
while(i != r->num)
{
r = r->next;
}
DList p = r->next;
//从链表中删除节点
r->next->next->prev = r;
r->next = r->next->next;
free(p);
//顺延链表节点i后的节点的序号
int n = i;
while(r->next)
{
r->num = n++;
r = r->next;
}
r->num = n;//尾节点的序号
list->num = dlist_size(list);//将创建链表的大小写入头结点num成员
}

5、获取双链表的长度

unsigned int dlist_size(DList list)
{
unsigned int count = 0;
DList p = list->next;
while(p)
{
p = p->next;
count++;
}
return count;
}

6、判断双链表是否为空

int dlist_is_empty(DList list)
{
if(list)
{
fprintf(stdout, "list is no empty.\n");
return 0;
}
else
{
fprintf(stdout, "list is empty.\n");
return 1;
}
}

7、遍历双链表

void dlist_traverse(DList list)
{
fprintf(stdout, "list size is %u\n", list->num);
DList p = list->next;//跳过头结点
while(p)
{
fprintf(stdout, "num = %u, id = %u, name = %s, subject = %s, score = %u\n", p->num, p->data.id, p->data.name, p->data.subject, p->data.score);
p = p->next;
}
}

8、双链表的翻转（逆序、倒序）

void dlist_reverse(DList list)
{
if(dlist_is_empty(list))
{
fprintf(stdout, "The list is empty.No reverse.\n");
return ;
}
DList prev, current, pnext;
current = list->next;//跳过头节点，当前节点为第一个节点
pnext = current->next;//当前节点的下一个节点
current->next = NULL;//当前节点断开后续连接，作为尾节点
while(pnext)
{
prev = pnext->next;//将当前节点的下一个节点作为当前节点的前一个节点
pnext->next = current;//当前节点的前一个节点的指针域指向当前节点
current = pnext;//将下一个节点作为当前节点
pnext = prev;//前一个节点作为下一个节点
}
list->next = current;//头结点指针域指向当前节点，完成逆序
//重新给逆序后的各节点赋值新的序号
int i = 1;
while(current)
{
current->num = i++;
current = current->next;
}
}

代码见附件。

附件：http://down.51cto.com/data/2367825