TestBook testseries linkedList question

Question

What does the following routine do on doubly linked list. M is some middle node address and N is a newly inserted node address.

N → lptr = M ;

N → rtptr = M → rptr ;

N → lptr → rptr = N ;

N → rptr → lptr = N ;

Inserts a node to

• A. Right of M
• B. Left of M
• C. Right Most
• D. Left Most

Comments

I didn’t get those pointer Iptr and rptr .

Hence couldn’t able to use it.

Answer 1

Here it is just inserting a new node $N$ in right of $M$.

as it is a Doubly Linked List , so it has two pointers , one pointing to the previous node $(Lptr)$ and the other point to the next node$(Rptr)$.

in this case ,

$N → lptr = M ;$

The previous pointer of $N$ is pointed to $M$.

$N → rtptr = M → rptr ;$

Now, the next pointer of $N$ is pointed to that node to which the next pointer of $M$ was pointing .

$N → lptr → rptr = N ;$

The next pointer of $M$ is pointing to $N$ ( as the previous pointer of $N$ is  nothing but $M$)

$N → rptr → lptr = N ;$

The , previous pointer of next node of $N$ is now pointing to $N$.