20 Priority Queue Interview Questions and Answers

A priority queue is a data structure that allows for efficient retrieval and manipulation of data. This makes it a popular choice for many applications, especially those that require real-time processing. When interviewing for a position that will use priority queues, it is important to be able to demonstrate your understanding of the data structure and its algorithms. This article discusses some common interview questions about priority queues and how to answer them.

Priority Queue Interview Questions and Answers

Here are 20 commonly asked Priority Queue interview questions and answers to prepare you for your interview:

1. What is a priority queue?

A priority queue is a data structure that allows you to store data in a way that makes it easy to retrieve the data in order of priority. This is often used in situations where you need to process data in a certain order, but the order in which the data is received is not necessarily the order in which it needs to be processed.

2. Can you explain the difference between a heap and a priority queue in Python?

A heap is a data structure that allows you to keep track of the smallest or largest element in a collection. A priority queue is a data structure that allows you to keep track of elements in a collection according to their priority.

3. How do you create a new queue in Python?

You can create a new queue in Python by using the Queue class.

4. How can you check if a queue is empty or not?

You can check if a queue is empty by using the isEmpty() function.

5. What are some ways to add items to a queue in python?

There are a number of ways to add items to a queue in python. One way is to use the put() method, which will add an item to the queue. Another way is to use the insert() method, which will add an item to the queue at a specific index.

6. How would you remove an element from a priority queue?

In order to remove an element from a priority queue, you would need to first find the element that you want to remove. You can do this by either searching through the queue until you find the element, or by keeping track of the element’s location in the queue. Once you have found the element, you would then need to remove it from the queue and adjust the queue accordingly.

7. Do all queues have priorities? If not, then which ones don’t?

Not all queues have priorities. In fact, most queues are first-in-first-out (FIFO), meaning that the order in which items are added to the queue is the order in which they are removed. However, some queues, such as priority queues, do have priorities, meaning that items are removed in order of their priority, not their order of addition.

8. Which modules should I use when creating a priority queue in python?

The most popular modules used for creating priority queues in python are the Queue and PriorityQueue modules.

9. What do you understand by “heap sort” in Python?

Heap sort is a sorting algorithm that uses a binary heap data structure. It is a comparison-based sorting algorithm, and it can be used to sort a list of integers or a list of strings.

10. Is it possible to convert a list to a queue in python? If yes, then how?

Yes, it is possible to convert a list to a queue in python. You can do this by using the collections module and importing the deque class. Then, you can create a new deque object and pass your list into it.

11. What’s the best way to check for existence of elements in a queue?

The best way to check for existence of elements in a queue is to use the peek() method. This method will return the element at the front of the queue without removing it.

12. How does the Queue module behave differently from the PriorityQueue module?

The Queue module is a first-in-first-out queue, meaning that the first element added to the queue will be the first one removed. The PriorityQueue module, on the other hand, is a priority queue, meaning that elements are removed in order of priority, with the highest priority element being removed first.

13. What are the different types of heaps that exist?

There are two main types of heaps: min heaps and max heaps. A min heap is one where the root node is always the minimum element in the heap, and a max heap is one where the root node is always the maximum element in the heap. There are also variations on these, such as min-max heaps and d-ary heaps, but the two main types are min and max.

14. What is the default ordering used by the PriorityQueue class? Can this be changed?

The default ordering used by the PriorityQueue class is the natural ordering of the elements. This can be changed by specifying a custom Comparator when creating the PriorityQueue.

15. How can we check the number of elements present in a queue?

We can use the size() function to check the number of elements in a queue.

16. What happens when we hit the maxsize limit on a queue in python?

When the maxsize limit is hit on a queue in python, the program will raise a Full exception.

17. Are there any other implementations of queues available besides FIFO?

There are a few other implementations of queues available, but the most common one is the priority queue. In a priority queue, items are given a priority, and they are dequeued in order of that priority. This can be useful in a number of situations, such as when you want to prioritize certain items over others.

18. What is the importance of maxsize in a queue?

The maxsize parameter is used to set the maximum number of items that can be stored in the queue. This is important because it helps to ensure that the queue does not become overloaded and that items are processed in a timely manner.

19. What is the maximum size allowed for a queue?

The maximum size of a queue is typically dictated by the amount of available memory.

20. Can we delete an element from the middle of a queue?

No, we cannot delete an element from the middle of a queue. We can only delete elements from the front or back of the queue.