Insert at End of Circular Linked List in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new node with the given value.

DSA C++

Node* newNode = new Node([1]);

Drag options to blanks, or click blank then click option'

Ahead

Bvalue

Cnullptr

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Using head or tail instead of the value.

Assigning nullptr instead of the value.

We create a new node with the given value to insert it at the end.

2fill in blank

medium

Complete the code to handle the empty list case by pointing newNode to itself.

DSA C++

if (head == nullptr) {
    newNode->next = [1];
    head = newNode;
    return;
}

Drag options to blanks, or click blank then click option'

Anullptr

Btail

Chead

DnewNode

Attempts:

3 left

💡 Hint

Common Mistakes

Setting next to nullptr breaks the circular property.

Using head or tail which may be null.

In a circular linked list with one node, the node points to itself.

3fill in blank

hard

Fix the error in the loop that finds the last node before head.

DSA C++

Node* temp = head;
while (temp->next != [1]) {
    temp = temp->next;
}

Drag options to blanks, or click blank then click option'

Ahead

Bnullptr

CnewNode

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for nullptr instead of head.

Using newNode or tail which are not defined here.

In a circular linked list, the last node points back to head, so we loop until next is head.

4fill in blank

hard

Fill both blanks to insert newNode at the end and maintain circular links.

DSA C++

temp->next = [1];
newNode->next = [2];

Drag options to blanks, or click blank then click option'

AnewNode

Bhead

Cnullptr

Dtemp

Attempts:

3 left

💡 Hint

Common Mistakes

Setting newNode->next to nullptr breaks the circle.

Not updating temp->next to newNode.

The last node's next points to newNode, and newNode's next points back to head.

5fill in blank

hard

Fill all three blanks to complete the insert function for circular linked list.

DSA C++

void insertEnd(Node*& head, int value) {
    Node* newNode = new Node([1]);
    if (head == nullptr) {
        newNode->next = [2];
        head = newNode;
        return;
    }
    Node* temp = head;
    while (temp->next != [3]) {
        temp = temp->next;
    }
    temp->next = newNode;
    newNode->next = head;
}

Drag options to blanks, or click blank then click option'

Avalue

BnewNode

Chead

Dnullptr

Attempts:

3 left

💡 Hint

Common Mistakes

Using nullptr instead of newNode or head.

Not looping until temp->next equals head.

Create newNode with value, point newNode to itself if list empty, loop until last node points to head.

Practice

1. What happens when you insert a new node at the end of an empty circular linked list?

easy

A. The new node points to itself, becoming the only node in the list.

B. The new node points to null, ending the list.

C. The new node is discarded because the list is empty.

D. The new node points to the head, but the list remains empty.

Solution

1. Step 1: Understand circular linked list empty state

   When the list is empty, there is no node, so the new node must point to itself to form a circle.

2. Step 2: Insert new node and update pointers

   The new node's next pointer is set to itself, making it the only node and the head of the list.

3. Final Answer:

   The new node points to itself, becoming the only node in the list. -> Option A

4. Quick Check:

   Empty list insertion creates a self-pointing node [OK]

Hint: New node points to itself if list is empty [OK]

Common Mistakes:

• Setting next pointer to null instead of itself
• Not updating the head pointer
• Assuming list remains empty after insertion

2. Which of the following is the correct syntax to insert a new node at the end of a circular linked list in C++?

easy

A. newNode->next = head; tail->next = newNode; tail = newNode;

B. newNode->next = nullptr; tail->next = newNode; tail = newNode;

C. newNode->next = tail; head->next = newNode; tail = newNode;

D. newNode->next = head; head->next = newNode; tail = newNode;

Solution

1. Step 1: Set new node's next to head

   In a circular linked list, the last node points to the head, so newNode->next = head.

2. Step 2: Update current tail's next and tail pointer

   Set tail->next to newNode to link the last node to new node, then update tail to newNode.

3. Final Answer:

   newNode->next = head; tail->next = newNode; tail = newNode; -> Option A

4. Quick Check:

   New node points to head, tail updated [OK]

Hint: Tail's next must point to new node, new node points to head [OK]

Common Mistakes:

• Setting newNode->next to nullptr instead of head
• Updating head->next instead of tail->next
• Not updating tail pointer after insertion

3. Given the circular linked list with nodes 10 -> 20 -> 30 -> (back to 10), what will be the list after inserting 40 at the end?

medium

A. 40 -> 10 -> 20 -> 30 -> (back to 40)

B. 10 -> 20 -> 30 -> (back to 40)

C. 10 -> 20 -> 30 -> 40 -> null

D. 10 -> 20 -> 30 -> 40 -> (back to 10)

Solution

1. Step 1: Identify current circular list structure

   The list is 10 -> 20 -> 30, and 30 points back to 10 forming a circle.

2. Step 2: Insert 40 at end and update pointers

   New node 40 points to head (10), old tail (30) points to 40, making list 10 -> 20 -> 30 -> 40 -> back to 10.

3. Final Answer:

   10 -> 20 -> 30 -> 40 -> (back to 10) -> Option D

4. Quick Check:

   New node added at end, circle maintained [OK]

Hint: New node points to head, old tail points to new node [OK]

Common Mistakes:

• Breaking the circle by pointing last node to null
• Inserting new node at start instead of end
• Not updating tail pointer

4. What is wrong with this code snippet for inserting at the end of a circular linked list?

void insertEnd(Node*& tail, int data) {
  Node* newNode = new Node(data);
  newNode->next = tail->next;
  tail = newNode;
}

medium

A. It sets newNode->next to null instead of head.

B. It deletes the old tail node accidentally.

C. It does not update the old tail's next pointer to newNode.

D. It inserts the new node at the beginning instead of the end.

Solution

1. Step 1: Check pointer updates in code

   The code sets newNode->next to tail->next (head), but does not update tail->next to newNode.

2. Step 2: Identify missing link update

   Without updating old tail's next pointer, the list breaks the circle and newNode is not linked properly.

3. Final Answer:

   It does not update the old tail's next pointer to newNode. -> Option C

4. Quick Check:

   Old tail's next must point to new node [OK]

Hint: Always update old tail's next to new node [OK]

Common Mistakes:

• Forgetting to update old tail's next pointer
• Setting newNode->next incorrectly
• Not updating tail pointer after insertion

5. You have a circular linked list with nodes 5 -> 15 -> 25 -> (back to 5). You want to insert a new node with value 35 at the end. After insertion, you mistakenly forget to update the tail pointer to the new node. What will be the effect on the list?

hard

A. The list will have 5 -> 15 -> 25 -> (back to 5) without 35.

B. The list will have 5 -> 15 -> 25 -> 35 -> (back to 5), but tail still points to 25.

C. The new node 35 will not be linked and will be lost.

D. The list will break and become linear ending at 25.

Solution

1. Step 1: Insert new node and link old tail

   New node 35 is linked after 25, and points back to head (5), so list is 5 -> 15 -> 25 -> 35 -> back to 5.

2. Step 2: Tail pointer not updated

   Tail still points to 25, so operations relying on tail may behave incorrectly, but list structure is intact.

3. Final Answer:

   The list will have 5 -> 15 -> 25 -> 35 -> (back to 5), but tail still points to 25. -> Option B

4. Quick Check:

   Tail pointer must update, else points to old last node [OK]

Hint: Tail pointer must update to new node after insertion [OK]

Common Mistakes:

• Assuming list breaks without tail update
• Thinking new node is lost if tail not updated
• Confusing tail pointer with node links