Traversal of Circular Linked List in DSA C# - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start traversal from the head node.

DSA C#

Node current = [1];

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

Anext

Bhead

Cnull

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Starting traversal from tail instead of head

Using null as starting point

Traversal of a circular linked list starts from the head node.

2fill in blank

medium

Complete the code to move to the next node during traversal.

DSA C#

current = current.[1];

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

Atail

Bprev

Chead

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next'

Using 'head' or 'tail' incorrectly

To traverse a linked list, move to the next node from the current node.

3fill in blank

hard

Fix the error in the loop condition to stop traversal after one full cycle.

DSA C#

do {
    Console.WriteLine(current.data);
    current = current.next;
} while (current != [1]);

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

Ahead

Bnull

Ctail

Dcurrent

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for null which never occurs in circular list

Using tail instead of head in condition

Traversal stops when current reaches back to the head node, completing one full cycle.

4fill in blank

hard

Fill both blanks to correctly print all nodes including the head once.

DSA C#

do {
    Console.WriteLine(current.data);
    current = current.[1];
} while (current != [2]);

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

Anext

Bhead

Cprev

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next'

Stopping at tail instead of head

The do-while loop prints the current node's data, moves to the next node, and stops when it reaches back to the head.

5fill in blank

hard

Fill all three blanks to create a method that traverses and prints a circular linked list.

DSA C#

public void Traverse() {
    if (head == null) return;
    Node current = [1];
    do {
        Console.WriteLine(current.[2]);
        current = current.[3];
    } while (current != head);
}

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

Ahead

Bdata

Cnext

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Starting from tail instead of head

Printing 'next' instead of 'data'

Moving to 'tail' instead of 'next'

The method starts from head, prints the data of each node, moves to the next node, and stops after completing one full cycle.

Practice

1. What is the main difference between traversing a circular linked list and a singly linked list?

easy

A. In a circular linked list, traversal stops when the last node's next is null.

B. In a singly linked list, traversal stops when the first node is reached again.

C. In a singly linked list, traversal never ends.

D. In a circular linked list, traversal stops when the starting node is reached again.

Solution

1. Step 1: Understand traversal stopping condition for singly linked list

   Traversal stops when the next pointer is null, indicating the end of the list.

2. Step 2: Understand traversal stopping condition for circular linked list

   Traversal stops when the traversal reaches the starting node again, since the list loops back.

3. Final Answer:

   In a circular linked list, traversal stops when the starting node is reached again. -> Option D

4. Quick Check:

   Circular list stops at start node [OK]

Hint: Remember: circular list loops back to start node [OK]

Common Mistakes:

• Thinking traversal stops at null in circular list
• Confusing stopping conditions of singly and circular lists
• Assuming circular list has a null next pointer

2. Which of the following C# code snippets correctly starts traversal of a circular linked list from the head node?

easy

A. Node current = head; for (int i = 0; i < length; i++) { Console.WriteLine(current.Data); current = current.Next; }

B. Node current = head; while (current != null) { Console.WriteLine(current.Data); current = current.Next; }

C. Node current = head; do { Console.WriteLine(current.Data); current = current.Next; } while (current != head);

D. Node current = head; while (current.Next != null) { Console.WriteLine(current.Data); current = current.Next; }

Solution

1. Step 1: Identify correct loop structure for circular list traversal

   Traversal must use a do-while loop to ensure the head node is processed before checking the condition.

2. Step 2: Check condition to stop traversal

   Traversal stops when current node returns to head, so condition is current != head in while.

3. Final Answer:

   Node current = head; do { Console.WriteLine(current.Data); current = current.Next; } while (current != head); -> Option C

4. Quick Check:

   Use do-while with current != head [OK]

Hint: Use do-while loop to handle circular traversal [OK]

Common Mistakes:

• Using while loop without do causes skipping head node
• Checking for null in circular list causes infinite loop
• Using for loop without length in circular list

3. What will be the output of the following C# code snippet for a circular linked list with nodes containing data 10 -> 20 -> 30 -> (back to 10)?

Node head = new Node(10);
head.Next = new Node(20);
head.Next.Next = new Node(30);
head.Next.Next.Next = head;

Node current = head;
do {
    Console.Write(current.Data + " -> ");
    current = current.Next;
} while (current != head);
Console.WriteLine("null");

medium

A. 10 -> 20 -> 30 -> null

B. 10 -> 20 -> 30 -> 10 -> null

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

D. 10 -> 20 -> 30 -> 30 -> null

Solution

1. Step 1: Understand the circular linked list structure

   The list nodes are 10 -> 20 -> 30, and 30 points back to 10, making it circular.

2. Step 2: Trace the do-while traversal

   Traversal starts at 10, prints 10, moves to 20, prints 20, moves to 30, prints 30, then moves back to 10 which stops the loop.

3. Final Answer:

   10 -> 20 -> 30 -> null -> Option A

4. Quick Check:

   Traversal prints nodes once until back to head [OK]

Hint: Traversal prints nodes once until back to head [OK]

Common Mistakes:

• Printing extra nodes after loop ends
• Confusing circular list with linear list output
• Not stopping traversal at head node

4. Identify the error in the following C# code snippet that attempts to traverse a circular linked list:

Node current = head;
while (current != null) {
    Console.WriteLine(current.Data);
    current = current.Next;
    if (current == head) break;
}

medium

A. The while condition should check current != head instead of current != null.

B. The while condition should be do-while to include head node.

C. The break condition is missing to stop infinite loop.

D. The code will cause a null reference exception.

Solution

1. Step 1: Analyze the while loop condition

   The condition current != null is incorrect for circular linked list because next is never null.

2. Step 2: Identify correct stopping condition

   The loop should stop when current returns to head, so condition should be current != head.

3. Final Answer:

   The while condition should check current != head instead of current != null. -> Option A

4. Quick Check:

   Use current != head to stop traversal [OK]

Hint: Check for current == head, not null, in circular list [OK]

Common Mistakes:

• Using null check in circular list traversal
• Missing break condition causing infinite loop
• Using while instead of do-while causing skipped node

5. Given a circular linked list where each node contains an integer, write a method to find the sum of all node values. Which approach correctly handles the circular nature without infinite looping?

hard

A. Start at head, use while loop with condition current != null, add node data each iteration.

B. Start at head, use do-while loop adding node data, stop when current returns to head.

C. Start at head, use for loop with fixed length equal to number of nodes, add node data.

D. Start at head, use while loop with condition current.Next != null, add node data.

Solution

1. Step 1: Understand circular list traversal for summation

   Traversal must visit each node exactly once and stop when current returns to head to avoid infinite loop.

2. Step 2: Choose correct loop structure

   Using a do-while loop starting at head and stopping when current == head ensures all nodes are included once.

3. Final Answer:

   Start at head, use do-while loop adding node data, stop when current returns to head. -> Option B

4. Quick Check:

   Use do-while and stop at head for sum [OK]

Hint: Use do-while and stop when current == head [OK]

Common Mistakes:

• Using null checks causing infinite loops
• Missing last node in sum due to wrong loop
• Using for loop without knowing list length