Queue operations (enqueue, dequeue) in Data Structures Theory - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a queue in data structures?

A queue is a collection where elements are added at one end and removed from the other, following the First-In-First-Out (FIFO) principle.

beginner

What does the enqueue operation do in a queue?

Enqueue adds an element to the back (end) of the queue.

beginner

What does the dequeue operation do in a queue?

Dequeue removes and returns the element at the front (start) of the queue.

beginner

Why is the queue called FIFO?

Because the first element added is the first one to be removed, like a line where the first person in line is served first.

intermediate

What happens if you try to dequeue from an empty queue?

It usually causes an error or returns a special value indicating the queue is empty, because there is nothing to remove.

Which end of the queue does enqueue add an element to?

A Back (end)

B Front (start)

C Middle

D Random position

Enqueue always adds elements to the back of the queue.

What principle does a queue follow?

A Last-In-First-Out (LIFO)

B Random order

C First-In-First-Out (FIFO)

D Priority order

Queues follow FIFO, meaning the first element added is the first removed.

What does dequeue do?

A Checks if the queue is empty

B Removes the last element

C Adds an element to the queue

D Removes the front element

Dequeue removes the element at the front of the queue.

If a queue is empty, what happens when you try to dequeue?

A Adds a new element

B Returns an error or special value

C Removes a random element

D Nothing happens

Dequeue on an empty queue usually causes an error or returns a special value indicating emptiness.

Which real-life example best represents a queue?

A People waiting in line at a store

B A stack of plates

C Books on a shelf

D Randomly shuffled cards

People waiting in line is a classic example of a queue following FIFO.

Explain the enqueue and dequeue operations in a queue with a real-life example.

Think about how people join and leave a line.

What happens if you try to dequeue from an empty queue and why is it important to handle this case?

Consider what happens when you try to take something from an empty container.