Priority Queue Introduction and Concept in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this priority queue insertion sequence?

Consider a min-priority queue where smaller numbers have higher priority. Insert the numbers 5, 3, 8, 1 in this order. What is the state of the queue after all insertions?

DSA C

Insert 5
Insert 3
Insert 8
Insert 1
Print queue

A 8 -> 5 -> 3 -> 1 -> null

B 5 -> 3 -> 8 -> 1 -> null

C 3 -> 1 -> 5 -> 8 -> null

D 1 -> 3 -> 5 -> 8 -> null

💡 Hint

Remember, in a min-priority queue, the smallest element is always at the front.

In a min-priority queue, elements are arranged so that the smallest element is always at the front. After inserting 5, 3, 8, and 1, the queue orders them as 1 -> 3 -> 5 -> 8 -> null.

❓ Predict Output

intermediate

What is the output after removing the highest priority element?

Given a max-priority queue with elements 10, 20, 15, 30 inserted in that order, what is the state of the queue after one removal of the highest priority element?

DSA C

Insert 10
Insert 20
Insert 15
Insert 30
Remove highest priority
Print queue

A 20 -> 15 -> 10 -> null

B 30 -> 20 -> 15 -> 10 -> null

C 15 -> 10 -> null

D 10 -> 15 -> 20 -> null

💡 Hint

In a max-priority queue, the largest element is removed first.

The largest element 30 is removed first. The remaining elements are 20, 15, and 10 arranged to keep max priority order: 20 -> 15 -> 10 -> null.

🧠 Conceptual

advanced

Which data structure is best suited to implement a priority queue efficiently?

Choose the data structure that allows efficient insertion and removal of the highest priority element in a priority queue.

A Linked List

B Binary Heap

C Array

D Stack

💡 Hint

Think about which structure supports fast access to the highest priority element and efficient reordering.

Binary Heap is the best choice because it allows insertion and removal in O(log n) time, maintaining the heap property for priority queue operations.

🔧 Debug

advanced

What error occurs in this priority queue code snippet?

This code tries to remove an element from an empty priority queue. What error will it cause?

DSA C

PriorityQueue pq = new PriorityQueue();
pq.remove();

A UnderflowError

B No error, returns null

C IndexOutOfBoundsException

D NullPointerException

💡 Hint

Removing from an empty queue usually causes an underflow condition.

Removing from an empty priority queue causes an UnderflowError because there are no elements to remove.

🚀 Application

expert

How many elements remain after these operations on a min-priority queue?

Start with an empty min-priority queue. Insert 7, 2, 9, 4, then remove two elements. How many elements remain in the queue?

DSA C

Insert 7
Insert 2
Insert 9
Insert 4
Remove
Remove
Count elements

A 4

B 3

C 2

D 1

💡 Hint

Each removal deletes one element. Count carefully after all operations.

Four elements inserted, two removed, so 2 elements remain in the queue.