single linked list with head and tail pointers

**Dadu@** · 03-04-2022

I am trying to understand how the single linked list will design if we are using head and tail pointers in list. First node would be "head" of list and last node be "tail" of list.

In a case where no elements in list so head and tail should be NULL pointer.

What happens in case when first node created ?

Does the head pointer point to the first node of list ? I think yes

Does the tail pointer point to the first node of list ? I think yes

Does the first node point to the next node of list ? I think yes

**G4143** · 03-04-2022

**snip

Actually I'm a little confused.. Could you explain your design more?

My understanding of a single linked list is as follows:

The head is just the first node in the linked list.
The tail is just the nodes that follow the head.

if we have a linked list with 5 nodes:

node1->node2->node3->node4->node5

In this case node1 would be the head and node2->node3->node4->node5 would be the tail.

**laserlight** · 03-05-2022

Originally Posted by Dadu@

Does the head pointer point to the first node of list ? I think yes

Yes.

Originally Posted by Dadu@

Does the tail pointer point to the first node of list ? I think yes

Yes.

Originally Posted by Dadu@

Does the first node point to the next node of list ? I think yes

I think you're talking about the next pointer of the first node. Since the first node was only just created, there is no second node, hence the next pointer of the first node must be a null pointer.

Originally Posted by G4143

The head is just the first node in the linked list.
The tail is just the nodes that follow the head.

That's the Lisp car vs cdr concept, useful for recursive thinking. But in this context, the tail refers to the last element of the linked list.

**G4143** · 03-05-2022

If you are creating a 'simple' linked list then the structure for the node should be straight forward. The node structure should have a member for the data and a member for the next node. That's it.

Code:

typedef struct node* LL_NODE_PTR;

typedef struct node {
  int data;
  LL_NODE_PTR next;
} LL_NODE;

**G4143** · 03-05-2022

Originally Posted by laserlight

That's the Lisp car vs cdr concept, useful for recursive thinking. But in this context, the tail refers to the last element of the linked list.

Could you post a link to the context the OP and you are referring to?

**laserlight** · 03-05-2022

Originally Posted by G4143

Could you post a link to the context the OP and you are referring to?

The OP wrote it right there in post #1:

Originally Posted by Dadu@

First node would be "head" of list and last node be "tail" of list.

This is typically used when you want to have a constant time append operation for the linked list (in addition to constant time prepend).

**G4143** · 03-05-2022

Originally Posted by laserlight

The OP wrote it right there in post #1:

This is typically used when you want to have a constant time append operation for the linked list (in addition to constant time prepend).

OK! I see what the OP is after now.

**Dadu@** · 03-05-2022

Originally Posted by laserlight

Yes.

I think you're talking about the next pointer of the first node. Since the first node was only just created, there is no second node, hence the next pointer of the first node must be a null pointer.

Yes. I was talking about the next pointer of the first node

What happens in case when second node added in list

Does the head pointer point to the first node of list ? I think yes
Does the tail pointer point to the second node of list ? I think yes
Does next pointer of the first node point to the next node of list ? I think yes
I think pointer of second node point to NULL because this is last node in list.

if everything looks correct, I will try to write function for complete process

Code:

 #include<stdio.h>

#include<stdint.h>
#include<stdlib.h>

struct node 
{
    int data;
    struct node * next;
};


int main ()
{ 
   struct node * head = NULL;
   struct node * tail = NULL;
  
   return 0;
}

**laserlight** · 03-05-2022

Originally Posted by Dadu@

Does the head pointer point to the first node of list ? I think yes

Yes.

Originally Posted by Dadu@

Does the tail pointer point to the second node of list ? I think yes

Yes

Originally Posted by Dadu@

Does next pointer of the first node point to the next node of list ? I think yes

Yes, but that's a self-referential tautology and hence doesn't really mean anything useful. What you probably meant to say is that you think that the next pointer of the first node points to the second node of the list, and indeed that should happen.

Originally Posted by Dadu@

I think pointer of second node point to NULL because this is last node in list.

Yes.

**Dadu@** · 03-05-2022

Originally Posted by laserlight

Yes.

Yes, but that's a self-referential tautology and hence doesn't really mean anything useful. What you probably meant to say is that you think that the next pointer of the first node points to the second node of the list, and indeed that should happen.

I am stuck in function

Code:

#include<stdio.h>
#include<stdint.h>
#include<stdlib.h>

struct node 
{
    int data;
    struct node * next;
};


 // Type Function (Type) 
 struct node * current = malloc(sizeof(*current);
     
      if ( current != NULL )
      {
            current -> data = value;
            current -> next = ;
            
            if( head == NULL )
            {
                head = current ;     
            }
            
            else 
                
            {
                  tail = current ;
                        
            }
      }


int main ()
{ 
   struct node * head;
   struct node * tail;
  
   return 0;
}

**Salem** · 03-05-2022

> I am stuck in function
That's because it isn't a function.

Review your other threads, such as
How to link next node in linked list

**Dadu@** · 03-05-2022

Originally Posted by Salem

> I am stuck in function
That's because it isn't a function.

Review your other threads, such as
How to link next node in linked list

As I said I am trying to make function. That's not the complete function because I am stuck there. I am looking help to undestand what it takes and what it gives when it execute

**Salem** · 03-05-2022

Well it's not going anywhere until you do make it a function.

Just posting random lines out of context and says "it doesn't work" tells us nothing.

**Dadu@** · 03-05-2022

Originally Posted by Salem

Well it's not going anywhere until you do make it a function.

Just posting random lines out of context and says "it doesn't work" tells us nothing.

It's clear that I want to make function. I guess function will take three arguments. I don't have any idea if function needs to return value or it don't need to return anything

**G4143** · 03-05-2022

At the very least you should post a function signature and what you expect that function to do.

i.e.

Code:

struct linked_list create_empty_list(void) {
/*This function initializes and returns a struct linked_list*/
}

Thread: single linked list with head and tail pointers

Thread Tools

Search Thread

Display

single linked list with head and tail pointers

Similar Threads

Declaring head and tail for doubly linked list

Linked List - Add to Tail

"insert sort with head and tail pointers"

Linked List - Add to Tail

Another List Q - Seg fault on head-tail list

Tags for this Thread