Program inserting an element in single linked list

Question

#include<stdio.h>
#include<malloc.h>
struct node
{
    int data;
    struct node *next;
};
struct node* insert_beg(struct node *h,int x)
{
    struct node *t;
    printf("\n address = %u --- ",*h);
    t=(struct node *)malloc(sizeof(struct node));
    if(h==NULL)
    {
        t->data=x;
        t->next=NULL;
        h=t;
    }
    else
    {


        t->data=x;
        t->next=h;
        h=t;
    }
    return h;

}
void display(struct node *h1)
{
    struct node *t=h1;
    while(t->next!=NULL)
    {
        printf("%d->",t->data);
        t=t->next;
    }
}
int main()
{
    struct node *p=NULL;
    int a,ch=5;
    while(ch--)
    {

    printf("\n Enter data");
    scanf("%d",&a);
    p=insert_beg(p,a);
    display(p);
    }display(p);

}

The above is a code for inserting element in the begining of the single linked link list in c.

The code compiles successfuly but when i am trying to insert an element the system hangs up... Not to locate the error. Can anyone suggest the correction i need to done.

Is there any error in the expression mentioned below... Need help.

p=insert_beg(p,a);

What do you mean by "[i]s there any error in the expression mentioned below"? Do you mean that you get a build error on that line? Or do you mean you get a crash when you run the program? Or do you simply wonder if the line is correct (without actually building/running your program)? Please elaborate. If you get a crash at runtime, have you tried running a debug build in a debugger, to catch the crash in action and locate where it actually happens in your code? — Some programmer dude
– Some programmer dude, Commented Dec 19, 2016 at 15:26
delete printf("\n address = %u --- ",*h); Also at display : while(t->next!=NULL) --> while(t != NULL) — BLUEPIXY
– BLUEPIXY, Commented Dec 19, 2016 at 15:28
don't forget to free memory for the Node, I can see memory freak there in main() — Seek Addo
– Seek Addo, Commented Dec 19, 2016 at 15:32
If you want to print the address of the node you passed to your insert function, use the %p specifier instead of %u in your printf(), and don't dereference h (which is NULL for the first insert). In other words, print the value of the pointer (which is the address of the node if there is one), not the value of what it points to. — Dmitri
– Dmitri, Commented Dec 19, 2016 at 15:33
printf("\n address = %u --- ",*h); attempts to dereference a NULL pointer. Try printf("\n address = %p --- ", (void *) h); — chux
– chux, Commented Dec 19, 2016 at 15:33

Ravi varu · Accepted Answer · 2016-12-19 17:24:46Z

1

#include<stdio.h>
#include<malloc.h>
struct node
{
    int data;
    struct node *next;
};
struct node* insert_beg(struct node *h,int x)
{
    struct node *t;
    t=(struct node *)malloc(sizeof(struct node));
    if(h==NULL)
    {
        t->data=x;
        t->next=NULL;
        h=t;
    }
    else
    {
        t->data=x;
        t->next=h;
        h=t;
    }
    return h;
}
void display(struct node *h1)
{
     struct node *t=h1;
     while(t->next!=NULL)
     {
         printf("%d->",t->data);
         t=t->next;
     }
    printf("%d",t->data);
}
int main()
{
    struct node *p=NULL;
    int a,ch=5;
    while(ch>=0)
    {
        printf("\n Enter data:-");
        scanf("%d",&a);
        p=insert_beg(p,a);
        display(p);
        ch--;
    }
    display(p);

}

answered Dec 19, 2016 at 17:24

Ravi varu

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2 Comments

Pankti Over a year ago

I needed this code in my program. Helped me where I was stuck. Thanks for the help

Ajay Khetan Over a year ago

where did you strucked @Pankti

Paul Ogilvie · Accepted Answer · 2016-12-19 15:42:02Z

0

    while(t->next!=NULL)

should be:

    while(t!=NULL)

also, your insert function can be simplified to:

struct node* insert_beg(struct node *h,int x)
{
    struct node *t;
    t=(struct node *)malloc(sizeof(struct node));
    t->data=x;
    t->next=h;
    return t;
}

edited Dec 19, 2016 at 15:42

answered Dec 19, 2016 at 15:36

Paul Ogilvie

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Comments

Community · Accepted Answer · 2017-05-23 12:01:49Z

0

You have an error in:

printf("\n address = %u --- ",*h);

Trying to print an entire structure.

In general use a debbuger for this as explained here

You can compile your program with debug information as follows:

gcc -o main -g main.c

And run it in gdb:

gdb main

Type 'run' command inside gdb, if it fails you can use a 'backtrace' to get loads of information why. Get comfortable with gdb tutorials as the manual might scare you off at first.

edited May 23, 2017 at 12:01

CommunityBot

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answered Dec 19, 2016 at 15:29

pbn

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1 Comment

Ajay Khetan Over a year ago

I had dereference h which was initially assigned NULL value.

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