ISRO CSE 2017 | Question: 53

Question

In a doubly linked list the number of pointers affected for an insertion operation will be

• A. 4
• B. 0
• C. 1
• D. Depends on the nodes of doubly linked list

Comments

sir, Do we need to consider "Depends on the nodes of doubly linked list" same as "Depends on the NUMBER OF nodes of doubly linked list" ....

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It should be " depend on position of  node( where to insert) ".

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If we gonna think about the worst case it will be 4 which comes from option A.

But considering average case, it does depend upon the nodes of DLL. So question is Ambiguous.

Answer 1

Answer D)

case 1: If insertion in beginning (assume starting node's pointer name is start)

newnode->next=start;

newnode->prev=null;

start->prev=newnode;

start=newnode;

total change 4

case 2:insertion in middle(assume after some node x)

newnode->next=x->next;

newnode->prev=x;

x->next->prev=newnode;

x->next=newnode;

total change 4

case 3: insertion at the end (end node be x)

newnode->next=null;

newnode->prev=x;

x->next=newnode

total change 3

Comments

I think in case one only 3 pointers will change newnode->prevs will initially null and after insertion also null.

Answer 2

option D will be more correct because they are not giving number of nodes in doubly linked list.

Since if Number of nodes in DLL is more than 2 nodes and if we want to insert node in begining of DLL then it may affect 3 pointers.

if th number of nodes in DLL is one , then it mayaffect 2 pointers.

So ultimately it depends on number of nodes in DLL.........

Comments

@akash
yes it is D which is correct option .

In this question , nothing is mention where to insert so it depends on the nodes of doubly linked list .. the node where to insert .

hence D is the only correct option :)

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I do not think the question has any meaning :O

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Sir why do you think the question doesn't contain any meaning.

Answer should be 'D' until they tell it explicitly where we are inserting.

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If the number of nodes in DLL is one , then it may affect 3 pointers- (I)- Next pointer of old node. (II)- Prev pointer of new node. (III)- Next pointer of new node- It will point to Null.

Suggest me where am I wrong.

Answer 3

Option D..It depends whether to insert at 1st,middle or at last.

Answer 4

For insertions in the middle of the list, to splice in a new node as follows: A --- B ^^ splice M in here A.next = M M.prev = A B.prev = M M.next = B Hence four pointer assignments take place. However, if the insertion be at the head or tail, then only two pointer assignments would be needed: TAIL (insert M afterward) TAIL.next = M M.prev = TAIL

Ans: D