Queue operations (enqueue, dequeue) in Data Structures Theory - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding enqueue operation in a queue

What happens when you perform an enqueue operation on a queue that is not full?

A The new element is added to the back of the queue.

B The queue is cleared before adding the new element.

C The new element is added to the front of the queue.

D The new element replaces the front element of the queue.

💡 Hint

Think about where new items go in a queue.

In a queue, the enqueue operation adds a new element to the back (end) of the queue, preserving the order of elements.

🧠 Conceptual

intermediate

Effect of dequeue operation on queue size

If a queue has 5 elements and you perform one dequeue operation, how many elements remain in the queue?

A The queue becomes empty.

B 4 elements remain.

C 6 elements remain.

D 5 elements remain.

💡 Hint

Dequeue removes one element from the front.

Dequeue removes the front element, so the queue size decreases by one.

🔍 Analysis

advanced

Queue behavior after multiple operations

Consider an empty queue. You perform these operations in order: enqueue(10), enqueue(20), dequeue(), enqueue(30), dequeue(). What is the front element now?

A 10

B 20

C Queue is empty

D 30

💡 Hint

Track the queue step-by-step after each operation.

After enqueue(10) and enqueue(20), queue is [10, 20]. Dequeue removes 10, queue is [20]. Enqueue(30) adds 30, queue is [20, 30]. Dequeue removes 20, queue is [30]. So front is 30.

📋 Factual

advanced

Queue underflow condition

What error or condition occurs if you try to dequeue from an empty queue?

A Overflow error

B Syntax error

C Underflow error

D No error, returns last element

💡 Hint

Think about removing from an empty container.

Trying to remove an element from an empty queue causes an underflow error because there is nothing to remove.

❓ Reasoning

expert

Comparing queue implementations: array vs linked list

Which statement correctly compares the enqueue operation in a queue implemented with a linked list versus an array?

A Enqueue in a linked list queue is always faster because it never requires shifting elements.

B Enqueue in an array queue is always faster because arrays have fixed size.

C Enqueue in a linked list queue requires shifting elements, unlike arrays.

D Enqueue in an array queue never causes overflow.

💡 Hint

Consider how elements are added in both implementations.

In a linked list, enqueue adds a node at the end without shifting. In arrays, enqueue may require shifting elements if not using circular buffer, making linked list enqueue generally faster.