Data Structure Questions and Answers – Circular Linked List

This set of Data Structure Multiple Choice Questions & Answers (MCQs) focuses on “Circular Linked List”.

1. What differentiates a circular linked list from a normal linked list?
a) You cannot have the ‘next’ pointer point to null in a circular linked list
b) It is faster to traverse the circular linked list
c) In a circular linked list, each node points to the previous node instead of the next node
d) Head node is known in circular linked list
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2. How do you count the number of elements in the circular linked list?
a)

public int length(Node head)
{
	int length = 0;
	if( head == null)
		return 0;
	Node temp = head.getNext();
	while(temp != head)
	{
		temp = temp.getNext();
		length++;
	}
	return length;
}

b)

public int length(Node head)
{
	int length = 0;
	if( head == null)
		return 0;
	Node temp = head.getNext();
	while(temp != null)
	{
		temp = temp.getNext();
		length++;
	}
	return length;
}

c)

public int length(Node head)
{
	int length = 0;
	if( head == null)
		return 0;
	Node temp = head.getNext();
	while(temp != head && temp != null)
	{
		temp = head.getNext();
		length++;
	}
	return length;
}

d)

public int length(Node head)
{
	int length = 0;
	if( head == null)
		return 0;
	Node temp = head.getNext();
	while(temp != head && temp == null)
	{
		temp = head.getNext();
		length++;
	}
	return length;
}

3. What is the functionality of the following piece of code? Select the most appropriate.

public void function(int data)
{
	int flag = 0;
	if( head != null)
	{
		Node temp = head.getNext();
		while((temp != head) && (!(temp.getItem() == data)))
		{
			temp = temp.getNext();
			flag = 1;
			break;
		}
	}
	if(flag)
		System.out.println("success");
	else
		System.out.println("fail");
}

a) Print success if a particular element is not found
b) Print fail if a particular element is not found
c) Print success if a particular element is equal to 1
d) Print fail if the list is empty
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4. What is the time complexity of searching for an element in a circular linked list?
a) O(n)
b) O(nlogn)
c) O(1)
d) O(n²)
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5. Which of the following application makes use of a circular linked list?
a) Undo operation in a text editor
b) Recursive function calls
c) Allocating CPU to resources
d) Implement Hash Tables
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6. Choose the code snippet which inserts a node to the head of the list?
a)

public void insertHead(int data)
{
	Node temp = new Node(data);
	Node cur = head;
	while(cur.getNext() != head)
		cur = cur.getNext()
	if(head == null)
	{
		head = temp;
		head.setNext(head);
	}
	else
	{
		temp.setNext(head);
		head = temp;
		cur.setNext(temp);
	}
	size++;
}

b)

public void insertHead(int data)
{
	Node temp = new Node(data);
	while(cur != head)
		cur = cur.getNext()
	if(head == null)
	{
		head = temp;
		head.setNext(head);
	}
	else
	{
		temp.setNext(head.getNext());
		cur.setNext(temp);
	}
	size++;
}

c)

public void insertHead(int data)
{
	Node temp = new Node(data);
	if(head == null)
	{
		head = temp;
		head.setNext(head);
	}
	else
	{
		temp.setNext(head.getNext());
		head = temp;
	}
	size++;
}

d)

public void insertHead(int data)
{
	Node temp = new Node(data);
	if(head == null)
	{
		head = temp;
		head.setNext(head.getNext());
	}
	else
	{
		temp.setNext(head.getNext());
		head = temp;
	}
	size++;
}

7. What is the functionality of the following code? Choose the most appropriate answer.

public int function()
{
	if(head == null)
		return Integer.MIN_VALUE;
	int var;
	Node temp = head;
	while(temp.getNext() != head)
		temp = temp.getNext();
	if(temp == head)
	{
		var = head.getItem();
		head = null;
		return var;
	}
	temp.setNext(head.getNext());
	var = head.getItem();
	head = head.getNext();
	return var;
}

a) Return data from the end of the list
b) Returns the data and deletes the node at the end of the list
c) Returns the data from the beginning of the list
d) Returns the data and deletes the node from the beginning of the list
View Answer

8. What is the functionality of the following code? Choose the most appropriate answer.

public int function()
{
	if(head == null)
		return Integer.MIN_VALUE;
	int var;
	Node temp = head;
	Node cur;
	while(temp.getNext() != head)
	{
		cur = temp;
		temp = temp.getNext();
	}
	if(temp == head)
	{
		var = head.getItem();
		head = null;
		return var;
	}
	var = temp.getItem();
	cur.setNext(head);
	return var;
}

a) Return data from the end of the list
b) Returns the data and deletes the node at the end of the list
c) Returns the data from the beginning of the list
d) Returns the data and deletes the node from the beginning of the list
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9. Which of the following is false about a circular linked list?
a) Every node has a successor
b) Time complexity of inserting a new node at the head of the list is O(1)
c) Time complexity for deleting the last node is O(n)
d) We can traverse the whole circular linked list by starting from any point
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10. Consider a small circular linked list. How to detect the presence of cycles in this list effectively?
a) Keep one node as head and traverse another temp node till the end to check if its ‘next points to head
b) Have fast and slow pointers with the fast pointer advancing two nodes at a time and slow pointer advancing by one node at a time
c) Cannot determine, you have to pre-define if the list contains cycles
d) Circular linked list itself represents a cycle. So no new cycles cannot be generated
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