Linked List

Question 1

What does the following Java code snippet accomplish?

SLLNode snode = new SLLNode(“Cris”);
System.out.println(snode);

(Assuming toString() is not overridden in the SLLNode class.)

A. It throws a runtime error
B. It prints “Cris”
C. It prints the node’s info field
D. It prints the default object reference

Answer 1

D. It prints the default object reference

Question 2

What value does next hold in the last node of a singly linked list?

A. Zero
B. Previous node
C. Null
D. Head

Answer 2

C. Null

Question 3

Why is insertion at the head more efficient than insertion at the tail in a singly linked list?

A. It uses less memory
B. It requires no traversal
C. It avoids pointer updates
D. It automatically sorts the list

Answer 3

B. It requires no traversal

Question 4

Which operation inserts a new node at the beginning of a singly linked list?

A. pushBack()
B. insertAtHead()
C. insertAtTail()
D. append()

Answer 4

B. insertAtHead()

Question 5

What does the next pointer in a singly linked list node refer to?

A. The previous node
B. The head node
C. The tail node
D. The next node in the list

Answer 5

D. The next node in the list

Question 6

Which traversal method is used to visit all nodes in a singly linked list?

A. while (current != null)
B. do-while (current != head)
C. while (current.prev != null)
D. for (int i = 0; i < size; i++)

Answer 6

A. while (current != null)

Question 7

In a singly linked list, how is traversal typically performed?

A. Using array indices
B. By jumping to tail
C. By following next pointers
D. Using backward pointers

Answer 7

D. Using backward pointers

Question 8

Which pointer is updated when inserting at the head of a singly linked list?

A. head.prev
B. head.next
C. tail
D. newNode.next

Answer 8

D. newNode.next

Question 9

What is the default value of the head pointer in a newly created singly linked list?

A. null
B. -1
C. head.next
D. 0

Answer 9

A. null

Question 10

Which operation deallocates a singly linked list node?

A. remove()
B. new()
C. null()
D. delete()

Answer 10

D. delete()

Question 11

What is the time complexity of inserting a node at the head of a singly linked list?

A. O(1)
B. O(n)
C. O(log n)
D. O(n²)

Answer 11

A. O(1)

Question 12

What does the diagram [Pedro] → [Hudas] → null represent?

A. A singly linked list
B. A stack
C. A circular list
D. A doubly linked list

Answer 12

A. A singly linked list

Question 13

Consider the sequence:
SLLNode snode2 = new SLLNode(“Hudas”);
SLLNode snode1 = new SLLNode(“Pedro”, snode2);
snode1.next = null;
delete(snode2);

What is the effect of delete(snode2)?

A. It removes the head node from the list
B. It deletes the entire list
C. It sets snode2 to null
D. It deallocates the node containing “Hudas” from memory

Answer 13

D. It deallocates the node containing “Hudas” from memory

Question 14

Which operation allocates a new singly linked list node?

A. delete()
B. new()
C. null()
D. toString()

Answer 14

B. new()

Question 15

What does toString() return when called on a node?

A. A string describing the node’s info
B. The memory address
C. The pointer value
D. The next node

Answer 15

A. A string describing the node’s info

Question 16

What happens when you delete the head node in a singly linked list?

A. The list is reversed
B. The head pointer is moved to the next node
C. The head remains unchanged
D. The tail becomes null

Answer 16

B. The head pointer is moved to the next node

Question 17

What is the result of toString(snode1) if snode1 contains “Pedro”?

A. Pedro → Hudas
B. null
C. “Pedro”
D. “Hudas”

Answer 17

C. “Pedro”

Question 18

Which operation removes the first node of a singly linked list?

A. deleteFromHead()
B. pop()
C. clear()
D. dequeue()

Answer 18

A. deleteFromHead()

Question 19

What happens when snode1.next = null is executed?

A. The node becomes the tail
B. The list is reversed
C. The node is deleted
D. The link to the next node is broken

Answer 19

D. The link to the next node is broken

Question 20

What condition indicates that a singly linked list is empty?

A. size == 0
B. head == tail
C. head == null
D. head.next == null

Answer 20

C. head == null

Question 21

Which pointer must be updated when inserting a node between two existing nodes in a DLL?

A. Only the new node’s prev pointer
B. No pointers need to be updated
C. Only the new node’s next pointer
D. Both the new node’s next and prev pointers, and the adjacent nodes’ pointers

Answer 21

D. Both the new node’s next and prev pointers, and the adjacent nodes’ pointers

Question 22

Which traversal method is unique to doubly linked lists?

A. Backward traversal
B. Recursive traversal
C. Circular traversal
D. Forward traversal

Answer 22

A. Backward traversal

Question 23

What happens if prev is not updated during insertion?

A. The node is deleted
B. The node is skipped during traversal
C. The list becomes singly linked
D. The list becomes circular

Answer 23

B. The node is skipped during traversal

Question 24

What does a doubly linked list node contain?

A. Data and index
B. Data and two pointers
C. Data and one pointer
D. Only data

Answer 24

B. Data and two pointers

Question 25

Which condition correctly identifies an empty doubly linked list? A. head == null and tail == null B. head != null and tail != null C. head != null and tail == null D. head == null and tail != null

Answer 25

A. head == null and tail == null

Question 26

What does the diagram null ← A ↔ B ↔ C → null represent? A. Singly linked list B. Array C. Doubly linked list D. Circular list

Answer 26

C. Doubly linked list

Question 27

What is the result of traversing a DLL from tail to head? A. Reverse order B. Random access C. No output D. Sorted order

Answer 27

A. Reverse order

Question 28

How many pointer fields does each node in a DLL typically contain? A. One B. None C. Three D. Two

Answer 28

D. Two

Question 29

What is the advantage of DLL over SLL? A. Less memory usage B. Simpler implementation C. Faster memory allocation D. Bidirectional traversal

Answer 29

D. Bidirectional traversal

Question 30

What happens if you forget to update the prev pointer during deletion in a DLL? A. The head pointer is lost B. The deleted node remains accessible C. The list becomes circular D. Backward traversal breaks

Answer 30

D. Backward traversal breaks

Question 31

Which of the following is true about the tail node in a DLL? A. Its prev pointer points to the previous node B. It cannot be deleted C. It always has a non-null next pointer D. It is inaccessible from the head

Answer 31

B. It cannot be deleted

Question 32

What value does prev hold in the head node of a DLL? A. Null B. Tail C. Zero D. Head

Answer 32

A. Null

Question 33

What does the prev pointer in a DLL refer to? A. Null B. The previous node C. The head D. The next node

Answer 33

B. The previous node

Question 34

Which pointer allows backward traversal in DLL? A. prev B. tail C. next D. head

Answer 34

A. prev

Question 35

What is the result of inserting a node at the tail of an empty DLL? A. The node is discarded B. Only head is updated C. Both head and tail point to the new node D. Only tail is updated

Answer 35

C. Both head and tail point to the new node

Question 36

Which operation is typically more efficient in a DLL than in a singly linked list? A. Insertion at the head B. Deletion of a node when its pointer is given C. Searching for a value D. Traversal from head to tail

Answer 36

B. Deletion of a node when its pointer is given

Question 37

What is the correct sequence of pointer updates when deleting a middle node in a DLL? A. Set prev.next to node.next and next.prev to node.prev B. No updates are needed C. Set node.prev to null and node.next to null D. Update head and tail only

Answer 37

A. Set prev.next to node.next and next.prev to node.prev

Question 38

What is the primary advantage of a doubly linked list over a singly linked list? A. It allows traversal in both directions B. It is faster for all operations C. It does not require pointers D. It uses less memory

Answer 38

A. It allows traversal in both directions

Question 39

Which operation is easier in DLL than SLL? A. Deletion at tail B. Deletion of a middle node C. Insertion at head D. Traversal

Answer 39

B. Deletion of a middle node

Question 40

Which node in DLL has both prev and next as null? A. Middle B. Only node C. Head D. Tail

Answer 40

B. Only node