双向链表的基本操作

#include<stdio.h>
#include<stdlib.h>
typedef struct doubleLink
{
int data;
struct doubleLink *pre;
struct doubleLink *next;
}dnode;

//建立链表
dnode* createDLink()
{
dnode *head,*p,*s;
int x;
head = (dnode*)malloc(sizeof(dnode));
p = head;
while(1)
{
printf("please input the data: ");
scanf("%d",&x);
if(x != 0)
{
s = (dnode*)malloc(sizeof(dnode));
s ->data = x;
s-> pre = p;
p->next = s;
p=s;
}
else
break;
}
p->next = NULL;
head = head ->next;
head->pre = NULL;
return head;
}

//顺序、反序打印链表
void printDLink(dnode *head)
{
dnode *p,*s;
p = head;
printf(" left to right: \n");
while(p)
{
printf("%d  ",p->data);
s = p;  //为了到达链表的末尾
p = p->next;
}
printf("\n right to left: \n");
while(s)
{
printf("%d  ",s->data);
s = s->pre;
}
printf("\n \n");
}

//删除一个结点
dnode* deletedNode(dnode *head,int i)
{
dnode *p;
p = head;
if(p->data == i)
{
head = p->next;
head->pre = NULL;
free(p);
return head;
}

while(p)
{
if(p->data == i)
{
p->pre->next = p->next;
p->next->pre = p->pre;
free(p);
return head;
}
p = p->next;
}

printf("data not found \n");
return head;
}

//插入一个结点
dnode* insertdNode(dnode *head,int i)
{
dnode *p,*temp;
p = head;

temp = (dnode*)malloc(sizeof(dnode));
temp ->data = i;

if(i < p->data)
{
head = temp;
head->next = p;
head->pre = NULL;
p->pre = head;
return head;
}

while(p != NULL && i > p->data)
{
p = p->next;
}
if(i < p->data)
{
temp ->next = p;
temp ->pre = p->pre;
p ->pre->next = temp;
p ->pre = temp;
return head;
}else
{
p->next = temp;
temp ->pre = p;
temp ->next = NULL;
return head;
}
}

int  main()
{
dnode *head;
head = createDLink();
printDLink(head);

head = insertdNode(head,4);
head = deletedNode(head,3);
printDLink(head);
return 0;
}