value of strct object being overwritten

[Parul Bagadia]

I have written a code for linklist; the different operations on it; but at the time of insertion; it doesn't create a new strct object; it's overwritting the value.....
Just see if somebody can point out, what's wrong with it.
As, the complete code is quite big; m writting only the insertion part.
Here; first is my root node.
And i have made a functon, which accepts the value of first.

[CODE=c]//General insertion.
#include<stdio. h>
#include<stdlib .h>
struct linklist
{
int value;
struct linklist*next;
}* first;
void insertion(struc t linklist*first)
{
struct linklist* add=NULL;
add= (struct linklist*)mallo c(sizeof(struct linklist));
printf("\nEnter the no. you wish to add in link list\n");
scanf("\n %d",&add->value);
/*while(first!=N ULL)
{
first=first->next;
}
first=add;
add->next=NULL;*/
first->next=add;
add->next=NULL;
add=add->next;
}
//Display of list
void display(struct linklist* first)
{
printf("\nFollo wing are the elements you have added in the list till now\n");
while(first!=NU LL)
{
printf("\n%d\n" ,first->value);
first=first->next;
}
}[/CODE]
I know here it works only for two values........
But then if i write a code for more than one value; it doesnt diplay even a single value.
The commented code is what i thought should work for inserting different value; but if i go for it; display function doesn't even display 2 values......
So, for the time being i have commented it out.
I had also tried with if statements; but invain.
What i need here is to update the value of first->next; so that there will be link in the objects; and every time user calls insertion function; a new add object should get created.
And here its overwrittin .......
Tell me what to do.

[fual]

#include<stdio.h>
#include<stdlib.h>
struct linklist
{
  int value;
  struct linklist*next;
}* first;

void insertion(struct linklist*first) {
  struct linklist* add=NULL;
  add= (struct linklist*)malloc(sizeof(struct linklist));
  printf("\nEnter the no. you wish to add in link list\n");
  scanf("\n %d",&add->value);
  /*while(first!=NULL)
  {
  first=first->next;
  }
  first=add;
  add->next=NULL;*/
  first->next=add;
  add->next=NULL;
  add=add->next;
}

//Display of list
void display(struct linklist* first) {
  printf("\nFollowing are the elements you have added in the list till now\n");
  while(first!=NULL) {
    printf("\n%d\n",first->value);
    first=first->next;
  }
}

That's the first step. Rule number #1 format your code :)

[Parul Bagadia]

#include<stdio.h>
#include<stdlib.h>
struct linklist
{
  int value;
  struct linklist*next;
}* first;

void insertion(struct linklist*first) {
  struct linklist* add=NULL;
  add= (struct linklist*)malloc(sizeof(struct linklist));
  printf("\nEnter the no. you wish to add in link list\n");
  scanf("\n %d",&add->value);
  /*while(first!=NULL)
  {
  first=first->next;
  }
  first=add;
  add->next=NULL;*/
  first->next=add;
  add->next=NULL;
  add=add->next;
}

//Display of list
void display(struct linklist* first) {
  printf("\nFollowing are the elements you have added in the list till now\n");
  while(first!=NULL) {
    printf("\n%d\n",first->value);
    first=first->next;
  }
}

That's the first step. Rule number #1 format your code :)

That's a sign used for including directive

[Laharl]

No, he's using # as the symbol for 'number'. He's taking a roundabout way of saying 'use the provided CODE tags when posting code here so we can read it easily'.

[Parul Bagadia]

I'm not getting you....

[Banfa]

The easiest place to add a new value to a linked list is at the head

// Pseudo Code
void AddItem(void)
{
    Get New Item -> NewItem

    NewItem->next = head;
    head = NewItem;
}

[Parul Bagadia]

The easiest place to add a new value to a linked list is at the head

// Pseudo Code
void AddItem(void)
{
    Get New Item -> NewItem

    NewItem->next = head;
    head = NewItem;
}

No but i want it to get added after first and i want the sequence as the same as i go on adding.

[Banfa]

No but i want it to get added after first and i want the sequence as the same as i go on adding.

Do you mean after the first or at the end?

[Parul Bagadia]

Do you mean after the first or at the end?

after the first; and every new node should get added after the most recent one.

[Parul Bagadia]

I just want to know; what's wrong in my code. because according to me; my logic is correct.... or may be you can say i'm unable to point out the mistake.

[Parul Bagadia]

Does somebody gonna tell me wats wrong with this......... this is really my final post.

[Laharl]

If you were doing this yourself (no computer), how would you go through the list to get to the end to add a new one on? Translate that to code. Then compare it to what your current code does and you'll see why you're wrong.

[Parul Bagadia]

If you were doing this yourself (no computer), how would you go through the list to get to the end to add a new one on? Translate that to code. Then compare it to what your current code does and you'll see why you're wrong.

I couldn't reach till the end of my list; coz i didnt come out of the insertion thing.
but according to me the code to reach till the end of the list would be;
while(first!=NU LL)
{
first=first->next;
}
first=add;
add->next=NULL;
where first is my root node and add is the node which ill be adding recently.

[Banfa]

Sorry not sure what happened there but you fell off my radar somehow.

On your assertion that your logic is right but you have a mistake in your code then in this case
[CODE=c]
/*while(first!=N ULL)
{
first=first->next;
}
first=add;
add->next=NULL;*/
[/CODE]
It doesn't work because first is a local variable and setting it's value can not effect anything outside the function, like your list for instance.

[CODE=c]
first->next=add;
add->next=NULL;
add=add->next;
[/CODE]
And this doesn't work because you do not attempt to traverse the the list to find the insertion point you just overwrite the second item in the list with the item to add.

Of the 2 the 1st chunk of code is closer to what you actually need but you need to stop the loop 1 iteration earlier than you are.

[Parul Bagadia]

first is my global variable and not local;
and second thing;
first->next=add;
add->next=NULL;
add=add->next;
i know this doesnt traverse the list;i did that coz my code will at least display 2 valus; instead of one;
but i didnt understand whats wrong with my while loop.
I know its overwritting the values;
but there lies my whole problem, why is it overwritting?
in case if i comment out
; first->next=add;
add->next=NULL;
add=add->next;
and just stick to while loop it doesnt work...