Circular linked list in Data Structures Theory - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the structure of a circular linked list

Which of the following best describes a circular linked list?

A A linked list where nodes are arranged in a tree-like hierarchy.

B A linked list where each node points to a random node in the list.

C A linked list where the last node points back to the first node, forming a circle.

D A linked list where the last node points to null, indicating the end of the list.

💡 Hint

Think about what makes a linked list circular.

In a circular linked list, the last node connects back to the first node, creating a loop. This allows traversal to continue indefinitely.

📋 Factual

intermediate

Traversal behavior in circular linked lists

What happens if you traverse a circular linked list without a stopping condition?

A The traversal will skip some nodes randomly.

B The traversal will raise an error when it reaches the last node.

C The traversal will stop automatically after visiting all nodes once.

D The traversal will continue indefinitely, causing an infinite loop.

💡 Hint

Consider that the last node points back to the first node.

Because the last node links back to the first, traversing without a condition to stop will loop forever.

🚀 Application

advanced

Identifying the number of nodes in a circular linked list

Given a pointer to any node in a circular linked list, which method correctly counts the total number of nodes?

Data Structures Theory

function countNodes(node) {
  if (!node) return 0;
  let count = 1;
  let current = node.next;
  while (current !== node) {
    count++;
    current = current.next;
  }
  return count;
}

A Start at the given node, move to next nodes until you return to the starting node, counting nodes.

B Start at the given node, move to next nodes until you reach null, counting nodes.

C Start at the given node, count nodes until you find a node with next pointing to null.

D Start at the given node, count nodes until you find a node with next pointing to itself.

💡 Hint

Remember the last node points back to the first node.

Because the list is circular, you stop counting when you return to the starting node.

🔍 Analysis

advanced

Comparing circular and singly linked lists

Which of the following is a key advantage of a circular linked list over a singly linked list?

A It allows traversal from any node to all other nodes without restarting at the head.

B It uses less memory because it has no tail node.

C It automatically sorts the nodes in ascending order.

D It prevents infinite loops during traversal.

💡 Hint

Think about how the last node connects in each list type.

In a circular linked list, you can start at any node and reach all others by following next pointers, unlike singly linked lists which start at the head.

❓ Reasoning

expert

Detecting a circular linked list

Which algorithm correctly detects if a linked list is circular?

A Check if the head node's next pointer points to the tail node.

B Use two pointers moving at different speeds; if they meet, the list is circular.

C Count nodes until you reach a node pointing to itself.

D Traverse the list and check if any node's next pointer is null.

💡 Hint

Think about Floyd’s cycle detection method.

Using two pointers moving at different speeds (slow and fast), if they meet, it means the list loops back on itself, confirming circularity.