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error of double linked list .

Hello,everybody.
I have no idea to rectify my error.
Could everyone helps me to solve it,thanks all.
I am a fresh man.Thanks again.

head file:

/* head file for double linked list */

/* Filename H1.h */



#include <stdio.h>

#include <stdlib.h>

#define LEN sizeof(linklist) /* Define the length of linked list */



typedef struct link

{

        char data;

        struct link * pre;

        struct link * next;

}linklist;            /* Defint structure of linked list */

main file:

/* double linked list main file */

/* Filename double.cpp */

#include "H1.h"



linklist * create(void)   /* Define the Function to create linked list*/

{

        linklist * head=NULL;

        linklist * p1,* p2;

        int i=2;              /* Define the sequence number */

        p1=(linklist *)malloc(LEN);

        head->next=p1;

        p1->pre=head;

        printf("Member[1] :");

        scanf("%c",&p1->data);

        

        if(p1!=NULL)

        {

                do

                {

                        p2=(linklist *)malloc(LEN);

                        printf("Member[%d] :",i);

                        scanf("%c",&p2->data);

                        p2->pre=p1;

                        p1->next=p2;

                        p1=p2;

                }while(p1->data!='$');

                p1->next=NULL;

                return head;

        }

}

/////////////////////////////////////////////////

void display(linklist * head) /* Define the function to display linked list */

{

        linklist * tem;

        int j=1;

        if((tem=head->next)!=NULL)

        {

                printf("\n");

                while(tem)

                {

                        printf("Member[%d] :",j++);

                        printf("%c",tem->data);

                }

        }

        else

        {

                printf("head node error, exit now!\n");

                exit(0);

        } 

}



//////////////////////////////////////////////////

void main()

{

        linklist * test_head;

        test_head=create();

        display(test_head);

}

You might want to let us know what the error is, we are not all mind-readers.

One thing that will cause a problem is this line near the top of create

head->next=p1;

You have assigned the value of NULL to head and are then trying to dereference it, this will probably cause your program to shut down.

Note: I didn't look any further, there may be more problems, you need to give more information.

thank you Dark.
This is what I want to know.
I really didn't know where the error occured.But I have no more info about it. :(

You might not know where the error occurred, but you must know what sort of error it was. For example:
- Did the program not compile? (show the error messages)
- Did the program not link? (show the error messages)
- Did the program run but not produce the expected output? (show the output)
- Did the program run for a bit and then stop? (show any output or error)
- Did the program stop straight away? (show any error messages)
- Did the program connect to the net and buy stuff on ebay using your credit card? (show me what it bought, I might want some too).

Dark,I have completed.

/* linked list main file */

#include "H1.h"



linklist * create(linklist * point[2])   /* Define the Function to create linked list*/

{

        linklist * head,* tail;

        linklist * p1,* p2;

        int flag=0;

        int count=2;

        //linklist * point[2]; /* Deposit head and tail */

        p1=p2=(linklist *)malloc(LEN);

        printf("\nMember[1] :");

        scanf("%c",&p1->data);

        head=NULL;

        

        while(p1->data!='0')

        {

                flag++;

                if(flag==1)           /* the first node*/

                {

                        head=p1;

                        p1->pre=p1->next=NULL;

                }

                else                  /* other nodes except the first one */

                {

                        p2->next=p1;

                        p1->pre=p2;

                }

                p2=p1;

                p1=(linklist *)malloc(LEN);

                printf("Member[%d] :\n",count++);

                scanf("%c",&p1->data);

        }                         /* create nodes */



        p2->next=NULL;

        tail=p2;

        point[0]=head;

        point[1]=tail;

        return * point;

}

/////////////////////////////////////////////////

void dispAhead(linklist * head) /* Define the function to display linked list */

{

        linklist * tem;

        int j=1;

        if((tem=head)!=NULL)

        {

                printf("\n");

                while(tem)

                {

                        printf("Member[%d] :",j++);

                        printf("%c",tem->data);

                        tem=tem->next;

                }

        }

        else

        {

                printf("head node error, exit now!\n");

                exit(0);

        } 

}



//////////////////////////////////////////////////

void main()

{

        linklist * point[2];

        linklist * tem;

    tem=create(point);

        dispAhead(tem);



}