Heapsort is a comparison-based sorting technique used by computer scientists to arrange elements in a certain order. This is an important skill to have if you plan to have a career where you use data structures since it helps provide a fundamental understanding of how to organize values. As you prepare for your upcoming interview for a computer science position, it may be beneficial to review some of the most frequently asked heapsort questions so you can think about your responses to them.

In this article, we list some heapsort interview questions you may encounter, explain why interviewers ask them, discuss what to include in your answer and share some sample responses.

## 7 heapsort interview questions with sample answers

Here are some examples of heapsort interview questions with example responses:

### 1. What is a heap?

An employer may begin your technical interview by asking you to define certain computer science terms, such as heap. This shows that you have a basic understanding of data structures. Give a clear definition that explains what a heap is and its uses.

Example: “A heap is a specialized tree-based data structure used in computer science. This almost complete tree satisfies the heap property, which states that each node in a tree contains a key that’s equal to or more excrement than its parent’s key. A heap helps to organize all nodes in a specific order and access the minimum or maximum elements quickly.”

### 2. What is a binary heap, and how do you implement it?

Another important heap data structure to understand is a binary heap. When answering this, mention that this data structure helps provide the largest value as a max-heap and the smallest as a min-heap. Since this is a two-part question, make sure you describe both what a binary heap is and how you implement it.

Example: “Binary heap is a common implementation of a heap and priority queues. They are binary trees that are either max-heap or min-heap. A max-heap is when the key at root or parent is larger than all other keys present in the binary heap, while a min-heap is when the key root is the smallest.

To implement a binary heap, use an array. Place the root of the tree in position one of the array and the left child of any given node at position “n” in “2n.” You can place the right child of a node at position “n” at position “2n+1.” Finally, the parent of “a” node at position “n” goes at position “n/2.”

### 3. Can you explain how heapsort works?

An interviewer may ask you to explain heapsort to determine how much experience you have with using it. Knowing heap sort can help you prepare you to learn about heap data structure and other advanced concepts. In your answer, share how it helps maintain order. You can also provide an example of a time you used heapsort to help you find a value instantly.

Example: “Heapsort is a comparison-based sorting algorithm that shrinks the unsorted region by taking the largest elements and moving them to the sorted region. It visualizes the elements of the array as a heap and has the best possible running time. You can use this when you want to maintain order while extracting a minimum or maximum.”

### 4. How do you “heapify” a tree?

Understanding how to perform certain actions to data structures is important when applying for a computer science role. Being able to heapify a tree allows you to create a heap data structure from a binary tree. To answer this question, explain how to reshape a tree.

Example: “To heapfiy a binary tree, or reshape it, you select an input array and convert it into a complete binary tree. Then, create a heap from the binary tree.”

### 5. Can you share some differences between a heap and a stack? Which is better?

An employer may ask this question to see if you understand how to allocate memory in a C, C++ or Java program. Knowing the advantages and disadvantages of each method can help you create scalable programs more effectively. In your response, select a few ways that a heap and a stack are different and then explain which one is better.

Example: “One of the biggest differences between a heap and a stack is that a heap is a hierarchical data structure, whereas a stack is a linear data structure. Unlike stack, heap memory can become fragmented when blocks of memory become allocated and then freed. Heap also allows you to access variables globally while stack only accesses local variables. Based on these characteristics, I’d say a stack is better static memory allocation and heap is better for dynamic memory allocation.”

### 6. What are the steps of the heapsort algorithm?

Interviewers may ask this question to see if you understand the algorithm involved in a heapsort. Since this is an efficient method for sorting data, it’s important to know how to use it with a list of items. In your answer, outline the steps to take when using this algorithm.

Example: “The first step of the heapsort algorithm is to build a binary tree with the list of elements. Then you can transform the binary tree into a min-heap. Once you have the min-heap, delete the root element from it, using the heapify method. Next, place the deleted elements into the sorted list. You then repeat these steps until all the values are in your sorted list.”

### 7. What are some ways to implement priority queue?

This question helps an employer assess your knowledge about heapsort. It may be helpful to review the different data structures that help you do this. Since there are a variety of ways to implement priority queue, include a list in your answer.

Example: “You can use data structures to implement priority queue. Some data structures to use include balanced heap, binary heap, binary search tree, ordered array, ordered list, unoredered array and unordered list.”

I hope you find this article helpful.

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