双向链表的功能实现：初始化，插入，按位置插入，按位置删除，按值删除，遍历打印等

#include<stdio.h>

#include <stdlib.h>

#define F -1

typedef struct Node* node;

struct Node

{
node prior;
node next;
int value;

};

int init(node *head);                                          //初始化

int insert_tail(node head, int element);             // 尾插法

void printh(node head);                                    // 从头开始遍历打印

void printt(node head);                                     // 从尾开始遍历打印

int insert_head(node head, int element);          // 头插法

int insert_index(node head, int element, int index);  // 按位置插入

int length(node head);                                              // 计算链表长度

int delete(node head, int element);                            // 删除结点

main()                     

{
int i;
node head;
init(&head);
for (i = 0; i < 10; i++)
{
insert_tail(head, i);
}
printh(head);
printt(head);
for (i = 0; i < 10; i++)
{
insert_head(head, i);
}

    printh(head);
printt(head);
insert_index(head, 99, 5);

    printh(head);
printt(head);
delete(head, 1);

    printh(head);
printt(head);

}

int delete(node head, int element)

{
node t;
node temp = head;
while (temp->next != head)
{
if (temp->next->value == element)
{
t = temp->next->next;
t->prior = temp;
free(temp->next);

            temp->next = t;
}
else 
{
temp = temp->next;
}
}
return 0;

}

int length(node head)

{
node temp = head;
int count = 0;
while (temp->next != head)
{
count++;
temp = temp->next;
}
return count;

}

int insert_index(node head, int element, int index)

{
node temp = head;
node newnode = (node)malloc(sizeof(struct Node));
int i;
if (index < 0 || index > length(head))
printf("out of range");
for (i = 0; i < index; i++)
{
temp = temp->next;
}
newnode->value = element;
newnode->next = temp->next;
newnode->prior = temp;
temp->next->prior = newnode;
temp->next = newnode;
return 0;

}

int insert_head(node head, int element)

{
node newnode = (node)malloc(sizeof(struct Node));
if (NULL == newnode)
{
return F;
}
newnode->value = element;
newnode->prior = head;
newnode->next = head->next;
head->next->prior = newnode;
head->next = newnode;
return 0;

}

void printh(node head)

{
node temp = head;
while (temp->prior != head)
{
printf("%d  ", temp->prior->value);
temp = temp->prior;
}
printf("\n");

}

void printt(node head)

{
node temp = head;
while (temp->next != head)
{
printf("%d  ", temp->next->value);
temp = temp->next;
}
printf("\n");

}

int insert_tail(node head, int element)

{
node newnode = (node)malloc(sizeof(struct Node));
if (NULL == newnode)
{
return F;
}
newnode->value = element;
newnode->next = head;
head->prior->next = newnode;
newnode->prior = head->prior;
head->prior = newnode;
return 0;

}

int init(node *head)

{
node newnode = (node)malloc(sizeof(struct Node));
if (NULL == newnode)
{
return F;
}
newnode->value = 0;
newnode->prior = newnode;
newnode->next = newnode;
*head = newnode;

}

4000