CVS Health Software Engineer Interview Questions + Guide in 2024

As a leading health solutions company, CVS Health serves millions of clients in the US to improve their healthcare experience. Virtual healthcare solutions are booming right now, as the survey showed that 71% of people think that a virtual visit for health service is more convenient for them.

In keeping with this trend, CVS Health must have reliable, maintainable, and scalable software systems to support the needs of its growing number of clients. Therefore, they continuously look for software engineering talents who can design scalable and efficient software systems—and one of these talents could be you.

If you’re preparing for an interview for a software engineer role at CVS Health, you’ve come to the right place. This guide presents several frequently asked interview questions tailored to the software engineer position at CVS Health, complete with an example of how you can answer each of them.

As with many technical positions, the interview process for a software engineer position at CVS Health may vary in length and structure. However, it involves several stages, each conducted by different teams with different purposes.

Application and Resume Screening

The interview process at CVS Health starts with the recruitment team reviewing your application documents, such as your cover letter and resume. During this stage, the hiring team assesses whether your qualifications and skills meet the job requirements.

First Technical Round

If your qualifications align with their needs, they will invite you to the first technical round. This round is usually conducted online and involves live coding that tests your SQL and Python proficiency. The questions are similar to Interview Query’s coding questions or Leetcode.

Second Technical Round

In the second technical round, you’ll be given a case study to assess your critical thinking and problem-solving skills. The focus is not on the accuracy of your answer but on how you explain your thought process for solving a particular use case.

Third Technical Round

The third technical round is the final interview for a software engineer position at CVS Health. You’ll be asked behavioral questions to assess your interpersonal and communication skills. You’ll also have a chance to discuss your career goals and expectations for your potential role at the company.

The questions you might encounter in a software engineer interview at CVS Health vary, ranging from technical questions such as programming, data structures, algorithms, and software system design to behavioral questions that delve deeper into your personality. Therefore, in this section, we’ll look at typical interview questions you’ll face at CVS Health’s Software Engineer interview.

1. What is your quality assurance process for writing code, and how do you spot a bug in an application?

This question is asked in a software engineer position at CVS Health to assess your thought process to ensure the quality and reliability of the software you develop. A sign of a great software engineer is the ability to conceptualize and execute best practices in the field.

How to Answer

Outline your approach to quality assurance in software development and methods for identifying and addressing application bugs. In the process, discuss the use of various testing techniques, such as unit testing, integration testing, and system testing, as well as your adherence to coding standards and best practices.

Example

“In my quality assurance process for writing code, I follow a systematic approach to ensure the software is reliable and robust. This involves several key steps, starting with thorough code review and testing at various stages of the development lifecycle.

During the coding phase, I pay close attention to coding standards and best practices to ensure the readability, maintainability, and scalability of the codebase. I also use version control systems like Git to track changes and collaborate effectively with team members.

Once the code is written, I conduct unit tests to verify the functionality of individual components and modules. I use testing frameworks such as JUnit or NUnit to automate these tests and ensure comprehensive test coverage. Integration tests are then performed to verify the interaction between different modules and identify any integration issues.

At the system level, I conduct end-to-end testing to validate the application’s overall behavior and functionality. This involves testing the application in a production-like environment to simulate real-world usage scenarios and identify any potential bugs or performance issues.

In addition to automated testing, I also perform manual testing to explore edge cases and validate the user experience from a human perspective. I use debugging tools and techniques to spot bugs in the application, such as stepping through code, inspecting variables, and analyzing error logs.”

2. How do you prioritize tasks and stay organized when you have multiple deadlines?

This question checks your time management skills, ability to handle pressure, and organizational abilities. In big companies like CVS Health, it’s common for software engineers to juggle multiple projects and deadlines simultaneously. They want to know how you prioritize tasks and manage your time to ensure projects are completed on time.

How to Answer

Start by discussing your approach to prioritizing tasks and managing multiple deadlines. Your answer may include assessing the importance of each task, breaking down larger projects into smaller tasks, and using management tools. Then, highlight your ability to stay organized, maintain focus, and adapt to changing priorities as needed.

Example

“My approach to prioritizing multiple deadlines and staying organized involves several key strategies. I start by carefully assessing the urgency and importance of each task or project. I prioritize tasks based on factors such as project deadlines, stakeholder expectations, and potential impact on project outcomes.

Next, I break down larger projects into smaller, more manageable tasks and create a detailed timeline or schedule to track progress and allocate time effectively. I use tools like project management software or task lists to stay organized and keep track of each task’s progress.

Throughout the process, I regularly communicate with team members and project stakeholders to keep them informed of progress, discuss any challenges or roadblocks, and adjust priorities as needed. Collaboration and transparency are key to ensuring that everyone is aligned and working toward the same goals.

For example, in a previous project, we had multiple deadlines to meet for different application features. I worked closely with the project manager to prioritize tasks based on business priorities and deadlines. By breaking down the project into smaller milestones and regularly reviewing our progress, we were able to meet all of our deadlines and deliver a successful outcome.”

3. What would you do if you were assigned a project with a technology stack you’re not familiar with?

A commitment to continuous learning is a highly desirable trait in a software engineer. So, the interviewer will evaluate your adaptability, problem-solving skills, and willingness to learn new technologies. A big company like CVS Health may require its software engineers to work with various technologies and tools to accomplish different projects and initiatives.

How to Answer

Demonstrate a proactive and resourceful approach to learning new technologies. Specifically, discuss your strategies for quickly gaining proficiency in unfamiliar technology stacks. These could include using online resources, seeking guidance from colleagues or mentors, and experimenting with hands-on projects or tutorials. Don’t forget to highlight your ability to adapt your existing skills and knowledge to new contexts.

Example

“If I were assigned a project with a technology stack I’m not familiar with, my first step would be to conduct a thorough check to understand the fundamentals of the new technologies involved. I would utilize online resources such as documentation, tutorials, and online courses to quickly gain a basic understanding of the technology stack and its components.

Next, I would seek guidance from colleagues or mentors who have experience working with the technology stack. I would ask for recommendations on best practices, common pitfalls, and resources for further learning. Collaborating with experienced team members would not only help me learn faster but also foster teamwork and knowledge sharing within the team.

I would also set up a development environment and start experimenting with small, hands-on projects to gain practical experience with the new technologies. Hands-on learning is crucial for deepening my understanding and building confidence in working with unfamiliar technology stacks.”

4. What is your approach to resolving conflict with co-workers or external stakeholders, partially when you don’t really like them?

This question evaluates your interpersonal skills, conflict resolution abilities, and professionalism. At big companies like CVS Health, you’ll likely work on a cross-functional team with people with different expertise and perspectives toward problems. Understanding how you handle conflicts, especially in challenging situations where personal preferences may be involved, is essential for maintaining a positive work environment.

How to Answer

Highlight your ability to navigate conflicts diplomatically and professionally, even when personal feelings are involved. Then, discuss your approach to conflict resolution, emphasizing active listening, empathy, and communication skills.

Example

“My approach to resolving conflicts is centered on open communication, empathy, and mutually beneficial solutions.

First, I believe in active listening and seeking to understand everyone’s perspectives and concerns. By listening empathetically and acknowledging the validity of others’ viewpoints, I can build trust and rapport, even in challenging situations.

I also attempt to maintain professionalism and respect in all interactions, regardless of personal feelings. I avoid reacting impulsively or letting emotions dictate my actions, instead focusing on constructive communication and problem-solving.

When conflicts arise, I try to address them directly and transparently, discussing the issues at hand and brainstorming potential solutions collaboratively. I believe in finding win-win solutions that satisfy the needs and interests of all parties involved.

For example, in a recent project, there was a disagreement with a co-worker over the approach to a technical problem. Despite our differences in opinion, I initiated a one-on-one discussion to understand their concerns and share my perspective. Through open dialogue and compromise, we were able to find a solution that combined aspects of both approaches and improved the project’s outcome.”

5. How do you keep your coding workflow organized?

A software engineer with a structured approach to coding workflow is more likely to write quality code and meet project deadlines. As such, this trait is highly desirable for a company like CVS Health that values efficiency, productivity, and collaboration.

How to Answer

Start by describing your methods and tools for organizing your coding workflow. Then, discuss techniques for managing tasks, handling code changes, and collaborating with team members. Don’t forget to highlight your ability to prioritize tasks, maintain code documentation, and follow coding standards and best practices.

Example

“I keep my coding workflow organized by following a structured approach that helps me stay focused, productive, and efficient. One of the key tools I use is task management software like Jira or Trello, where I break down large tasks into smaller, manageable subtasks and track their progress throughout the development process. This allows me to prioritize my work effectively and ensures I stay on track to meet project deadlines.

In addition to task management, I also use version control like the Git branching strategy, such as GitFlow, to organize my code changes into feature branches, which helps keep the codebase clean and stable.

To maintain code quality and consistency, I always follow coding standards and best practices, such as following naming conventions, writing clear and concise code comments, and conducting code reviews with team members.“

6. You are given an N-dimensional array (a nested list), and your task is to convert it into a 1D array. The N-dimensional array can have any number of nested lists, and each nested list can contain any number of elements. The elements in the nested lists are integers. How can you write a function that takes an N-dimensional array as input and returns a 1D array?

Before applying for a software engineer position at CVS Health, be sure you have mastered programming and algorithmic concepts. This question assesses both of those concepts and your efficiency in implementing algorithms in code.

How to Answer

Demonstrate your understanding of recursion and nested data structures. Discuss an algorithmic approach to flatten the nested array, considering the possibility of nested lists of varying depths. Finally, explain how to traverse the nested array recursively, appending elements to a 1D array as they encounter them.

Example

“In order to convert an N-dimensional array into a 1D array, I would implement a recursive function that traverses the nested lists, appending elements to a 1D array as they are encountered. Here’s a high-level overview of the approach:

• Initialize an empty 1D array to store the flattened elements.
• Iterate through each element of the N-dimensional array.
• If the current element is an integer, append it to the 1D array.
• If the current element is a nested list, recursively call the function to flatten it.
• Return the flattened 1D array.

This approach ensures that we can handle nested lists of any depth, effectively flattening the N-dimensional array into a 1D array.“

def flatten_array(nested_array):

		flat_array = []
		
		for element in nested_array:
			if isinstance(element, list):
				flat_array.extend(flatten_array(element))
			else:
				flat_array.append(element)
	
		return flat_array

nested_array = [1, [2, [3, 4], 5], 6]
result = flatten_array(nested_array)

7. How would you decide which design pattern to use in a software development project?

Understanding software design pattern is critical to becoming a software engineer. Mastering it enables you to build a system that is performant, maintainable, and scalable. This question assesses your ability to make informed decisions when designing software systems.

How to Answer

Demonstrate your knowledge of different design patterns and when to apply each based on the specific requirements. Consider factors such as the complexity of the system, the need for flexibility and extensibility, and the familiarity of the team with different design patterns. Discuss the pros and cons of each pattern and justify your choice.

Example

“In deciding which design pattern to use, I would first carefully analyze the requirements and constraints of the problem we’re trying to solve. For example, if we’re developing a system that needs to handle multiple concurrent requests efficiently, the use of the singleton pattern might not be appropriate due to potential bottlenecks. In such cases, I would consider using the factory method pattern to delegate the responsibility of object creation to specialized factory classes, allowing for better scalability and flexibility.

Alternatively, if we’re working on a system that involves complex interactions between objects with different responsibilities, the use of the observer pattern could be beneficial for establishing loosely coupled communication between these objects, enabling easier maintenance and extensibility.

However, the final decision of the design pattern should be driven by a thorough understanding of the problem domain, the specific requirements of the project, and the trade-offs associated with each design pattern.”

8. Given an array filled with random values, how can you write a function to rotate the array 90 degrees clockwise?

This question assesses your understanding of array manipulation and algorithmic thinking. At CVS Health, daily duties involve data processing tasks that require understanding data structures like arrays.

How to Answer

Outline an algorithmic approach to rotating the matrix 90 degrees clockwise, such as transposing it. Explain the transpose of a matrix and how to reverse each row to achieve the requested rotation.

Example

“In order to rotate the matrix 90 degrees clockwise, I would implement a function that first transposes the matrix and then reverses each row. Here’s a high-level overview of the approach:

• Transpose the matrix by swapping elements across the diagonal.
• Reverse each row of the transposed matrix to achieve the 90-degree clockwise rotation.

This approach ensures that we can rotate the matrix efficiently without the need for additional space. Here’s a Python implementation of the function:”

import numpy as np
def rotate_matrix(matrix):
    # Transpose the matrix
    matrix = np.transpose(matrix)
    # Reverse each row
    matrix = np.flip(matrix, axis=1)
    return matrix
array = np.array([[1, 2, 3, 4, 5], [2, 3, 4, 5, 6], [3, 4, 5, 6, 7], [4, 5, 6, 7, 8], [5, 6, 7, 8, 9]])
rotated_array = rotate_matrix(array)

9. What is the difference between Test-Driven Development (TDD) and Behavior-Driven Development (BDD)?

Big companies like CVS Health rely on methodologies like TDD and BDD in their software development processes to ensure the quality and reliability of their healthcare software systems. So this question may be asked in a software engineer interview to check your understanding of these methodologies.

How to Answer

Explain the differences between Test-Driven Development (TDD) and Behavior-Driven Development (BDD). Specifically, describe the key principles, practices, and goals of each methodology, highlighting differences in their approaches to writing tests, specifying requirements, and fostering collaboration between development teams and stakeholders.

Example

“Test-driven development (TDD) and Behavior-Driven Development (BDD) are both software development methodologies that aim to improve the quality and maintainability of software systems, but they differ in their focus and approach.

TDD is a development approach where developers write tests for small units of code before writing the code itself. The primary goal of TDD is to ensure that each unit of code behaves as expected and that any changes to the codebase do not introduce bugs.

On the other hand, BDD is a broader approach that focuses on defining the software system’s behavior from the perspective of its stakeholders. BDD emphasizes collaboration between developers, QA engineers, and business stakeholders to ensure the software meets the desired behaviors and outcomes. Therefore, BDD tests typically focus on higher-level behaviors or features of the system, rather than individual units of code.”

10. Given two strings, how would you write a function that finds the longest common substring between the input strings?

One requirement for becoming a software engineer is problem-solving skills, especially when dealing with algorithmic problems. This question is asked to assess exactly that—they want to see your ability to solve algorithmic problems and how you ensure efficiency in your code.

How to Answer

Discuss an algorithmic approach to find the longest common substring between two input strings, such as iterating through the characters of the strings and identifying common substrings using dynamic programming or other efficient techniques.

Example

“To find the longest common substring between two input strings, I would implement a function that iterates through the characters of the strings and identifies common substrings using dynamic programming. Here’s a high-level overview of the approach:

• Initialize a 2D array to store the lengths of common substrings between characters of the two strings.
• Iterate through the characters of the strings and fill the array based on the lengths of common substrings.
• Identify the maximum length of common substrings and extract the longest common substring from the input strings.

Here’s a Python implementation of the function:”

def max_common_substring(string1, string2):
    m = len(string1)
    n = len(string2)
    dp = [[0] * (n + 1) for _ in range(m + 1)]
    max_length = 0
    end_index = 0
    for i in range(1, m + 1):
        for j in range(1, n + 1):
            if string1[i - 1] == string2[j - 1]:
                dp[i][j] = dp[i - 1][j - 1] + 1
                if dp[i][j] > max_length:
                    max_length = dp[i][j]
                    end_index = i
            else:
                dp[i][j] = 0
    return string1[end_index - max_length:end_index]
string1 = "Python"
string2 = "Phython"
result = max_common_substring(string1, string2)

11. What do you know about the MVC framework?

This question assesses your familiarity with common software design patterns and architectural principles. CVS Health uses frameworks like Model-View-Controller (MVC) in its software development projects to facilitate the development of modular applications.

How to Answer

Start by briefly explaining the MVC framework by highlighting its key components and principles. Then, describe the roles of the model, view, and controller components and how they interact with each other to handle user input, process data, and present the user interface. Also, discuss the benefits of using the MVC framework, such as improved code organization, separation of concerns, and easier maintenance and testing.

Example

“The Model-View-Controller (MVC) framework is a software architectural pattern commonly used in the development of web applications. It divides an application into three interconnected components:

• Model: The model represents the application’s data and business logic. It encapsulates the data and provides methods for accessing and manipulating it. The model is responsible for interacting with the database or other data sources and updating the view with any changes to the data.
• View: The view represents the presentation layer of the application. It is responsible for displaying the data to the user in a format that is easy to understand and interact with. The view receives input from the user and passes it to the controller for processing.
• Controller: The controller acts as an intermediary between the model and the view. It receives input from the user via the view, processes it, and updates the model accordingly. The controller then instructs the view to update its display based on any changes to the data.

The MVC framework promotes a separation of concerns, making it easier to manage and maintain complex applications. It also facilitates code reuse and modularity, as each component can be developed and tested independently.”

12. Given an (integer) height h and base b, how can you write a function that returns the shape of the isosceles triangle using (a 2D list) of 0s and 1s, where 0 and 1 represent the space outside and inside of the triangle, respectively?

This question checks your ability to work with data structures like 2D arrays and implement conditional logic. If you’d like to become a good software engineer, then work to demonstrate problem-solving skills and attention to detail, ensuring correctness and efficiency in your solution.

How to Answer

Consider implementing rules for constructing isosceles triangles, such as ensuring the base is odd and handling the filling of the triangle’s interior. Then, address edge cases where a valid triangle cannot be formed and return None in such cases.

Example

“In order to draw the isosceles triangle, I would first validate the input to ensure that the base is odd, as required for constructing an isosceles triangle. Then, I would initialize a 2D list to represent the triangle and use nested loops to fill in the appropriate values based on the triangle’s shape.

Here’s an algorithmic approach to solving the problem:

• Validate the input: Ensure that the base is odd. If not, return None.
• Initialize a 2D list to represent the triangle, filled with zeros.

Next, we Iterate over the rows of the triangle:

• Calculate the width of the current row based on its position.
• Calculate the starting index for filling in ones based on the width.
• Fill in ones within the calculated range to form the triangle’s shape.
• Return the constructed triangle.

Here’s a Python implementation of the function:”

def draw_isosceles_triangle(h, b):
    if b % 2 == 0:
        return None
   
    try:
      triangle = [[0] * b for _ in range(h)]
     
      for i in range(h):
          width = (i * 2) + 1
          start_index = (b - width) // 2
          for j in range(start_index, start_index + width):
              triangle[i][j] = 1
     
      return triangle
    except:
      return None

h = 2
b = 3
result = draw_isosceles_triangle(h, b)

13. What do you know about microservice and can you tell us in which use case we should use it?

When applying for a software engineer position at CVS Health, go into the interviews knowing different varieties of software architecture. This is necessary because the choice of software architecture will determine the maintainability and scalability of the software system later on. With this question, CVS wants to test your knowledge regarding one of the most used variants of software architecture.

How to Answer

Start by providing a concise explanation of microservices architecture and discuss the scenarios in which it is suitable. Then, highlight the benefits of microservices, such as increased agility, better fault isolation, and easier scalability; and explain how these benefits align with the requirements of specific use cases. Don’t forget to also discuss potential challenges and considerations when implementing microservices, such as managing communication between services and ensuring data consistency.

Example

“Microservices architecture is an approach to building software systems as a collection of small, independently deployable services, each responsible for a specific business function. These services communicate with each other through well-defined APIs, and each service can be developed, deployed, and scaled independently.

One of the key benefits of microservices is improved agility and scalability. By breaking down a monolithic application into smaller, more manageable services, teams can develop and deploy new features more quickly and scale individual services as needed to handle increased loads. This is particularly useful in healthcare applications, where different modules or functionalities may have varying scalability requirements.

Another use case for microservices is better fault isolation. In a monolithic architecture, a failure in one part of the application can bring down the entire system. With microservices, failures are isolated to individual services, allowing the rest of the system to continue functioning. This can be critical in healthcare applications where uptime and reliability are paramount.

However, it’s important to note that microservices also introduce challenges, such as managing communication between services, ensuring data consistency across distributed systems, and monitoring and debugging complex architectures.”

14. Given a list of integers, how can you write a function that finds the index at which the sum of the left half of the list is equal to the right half?

This question also assesses your ability to solve problems related to data structures and algorithmic thinking. As mentioned, demonstrating your proficiency in algorithm and code optimization is essential for becoming a software engineer at CVS Health.

How to Answer

Discuss algorithmic approaches such as iterating through the list, calculating the cumulative sums of both halves at each index, and checking for equality. If a matching index is found, it should be returned. If no such index is found, -1 should be returned.

Example

“To find the index where the sum of the left half of the list is equal to the right half, I would implement a function that iterates through the list, maintaining cumulative sums for both halves at each index. Here’s an algorithmic approach to solving the problem:

• Iterate through the list, maintaining cumulative sums for both the left and right halves.
• At each index, check if the cumulative sum of the left half is equal to the cumulative sum of the right half.
• If a matching index is found, return it. If no such index is found, return -1.

Here’s a Python implementation of the function:”

def equivalent_index(nums):
    total_sum = sum(nums)
    left_sum = 0
    for i in range(len(nums)):
        left_sum += nums[i]
        right_sum = total_sum - left_sum
        if left_sum == right_sum:
            return i
    return -1

nums1 = [1, 7, 3, 5, 6]
nums2 = [1, 3, 5]
result1 = equivalent_index(nums1)
result2 = equivalent_index(nums2)

15. Can you explain the concept of modularization?

The ability to develop modular software systems is crucial if you want to be a software engineer at CVS because modular software is easily maintained and scaled. Therefore, this question is to evaluate your understanding of software engineering principles.

How to Answer

Start by clearly explaining modularization and its significance in software development. Then, discuss how modularization involves breaking down a software system into smaller, self-contained modules or components, each responsible for a specific functionality or feature. Finally, mention all of the benefits of modularization.

Example

“Modularization is the process of breaking down a software system into smaller, independent modules or components, each serving a specific purpose or functionality. These modules are designed to be self-contained and loosely coupled, meaning they can be developed, tested, and maintained independently of other modules in the system.

This concept is crucial in software engineering because it allows for better organization and management of complex systems. Modularization allows developers to easily understand and maintain the codebase. It also promotes code reuse, as modules can be shared across different projects or teams.”

16. Let’s say you’re given a huge 100 GB log file and want to count the number of lines in it. How would you count them in Python?

Regardless of the programming languages you use in your software engineering projects later on, you’ll most likely be dealing with large files with hundreds or even thousands of lines of code. Therefore, this question aims to assess your problem-solving skills and how you can implement your solution effectively into the code.

How to Answer

First, consider memory constraints and ensure that the solution can handle files of any size without loading the entire file into memory. You can achieve this, for example, by using file iterators or reading the file line by line to minimize memory usage.

Example

“In order to count the total number of lines in a huge log file in Python, I would use a memory-efficient approach by reading the file line by line. Here’s how I would approach it:

• Open the log file in read mode.
• Initialize a counter variable to keep track of the number of lines.
• Iterate over each line in the file using a for loop or a file iterator.
• For each line, increment the counter by 1.
• Once all lines have been processed, close the file and return the total count.

Here’s a Python implementation of the approach:”

def count_lines_in_file(file_path):
    line_count = 0
    with open(file_path, 'r') as file:
        for line in file:
            line_count += 1
    return line_count

# Example usage:
log_file_path = 'path/to/log_file.log'
total_lines = count_lines_in_file(log_file_path

17. How would you normally implement software testing?

CVS Health values the quality and reliability of its software systems. When applying for a software engineer position at this company, understanding how to implement effective software testing is vital for ensuring that these systems meet requirements and perform as expected.

How to Answer

Start by discussing the different types of software testing methodologies and techniques, as well as the importance of testing throughout the software development lifecycle. Then, stress the need for a comprehensive testing strategy that includes unit, integration, system, and acceptance testing.

Example

“In a software development project, I would normally approach software testing in multiple phases, starting with unit testing to test individual components or modules of the software in isolation to ensure they perform as expected. I would follow this with integration testing to test the interaction between different components to verify they work together correctly.

Next, I would conduct system testing to check the entire system as a whole, ensuring that it meets the specified requirements and functions correctly in its intended environment. Finally, I would conduct acceptance testing to validate the software against user requirements to ensure it meets the needs of its stakeholders.”

18. Given the root of a binary search tree (BST) and certain rules to define what a valid BST actually is, how would you write a function to determine if a BST is valid or not?

Understanding data structures and algorithms is crucial if you want to become a software engineer at any company, including CVS Health. Therefore, this question is asked to assess your knowledge about one of the most common hierarchical data structures—the binary tree.

How to Answer

Demonstrate your understanding of the properties of a valid binary search tree and develop an algorithm to verify if a given binary tree satisfies these properties. This typically involves performing a depth-first search (DFS) traversal of the tree while keeping track of the range of valid values for each node. At each node, check if the node’s value falls within the valid range determined by its parents.

Example

“To determine if a binary tree is a valid binary search tree (BST), I would implement a depth-first search (DFS) traversal algorithm while keeping track of the valid range of values for each node. Here’s how I would approach it:

• Implement a recursive helper function that takes three parameters: the current node, the lower bound, and the upper bound of the valid range of values.
• At each node, check if its value is within the valid range determined by its parents.
• Recursively traverse the left subtree with updated upper bound and lower bound parameters based on the current node’s value.
• Recursively traverse the right subtree with updated upper bound and lower bound parameters based on the current node’s value.
• If a node’s value violates the BST property at any point, return False. Otherwise, return True at the end of the traversal.

Here’s a Python implementation of the approach:”

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def is_valid_bst(root: TreeNode) -> bool:
    def helper(node, lower=float('-inf'), upper=float('inf')):
        if not node:
            return True
        if node.val <= lower or node.val >= upper:
            return False
        return helper(node.left, lower, node.val) and helper(node.right, node.val, upper)
    
    return helper(root)
root = TreeNode(2)
root.left = TreeNode(1)
root.right = TreeNode(3)
print(is_valid_bst(root))  # Output: True

19. Can you explain the concept of object-oriented programming (OOP)?

Your ability to write clean code is crucial to becoming a good software engineer. Object-oriented programming (OOP) is one of the coding best practices. Since CVS Health implements the OOP paradigm in its software development projects, be sure you know it.

How to Answer

Start by clearly explaining OOP concepts and principles. Then, discuss how OOP allows for the creation of software systems based on objects, which encapsulate data and behavior, and how these objects interact with each other through defined interfaces. Finally, explain the benefits of OOP, such as code reusability, modularity, and easier maintenance.

Example

“In OOP, classes serve as blueprints for creating objects. A class defines the properties (attributes or fields) and behaviors (methods or functions) that all objects of that class will have. Objects can interact with each other by sending messages or invoking methods.

OOP is based on several key principles, such as encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation refers to the bundling of data and methods within a class, which helps hide the internal implementation details and provides a clean interface for interacting with objects.
• Inheritance allows for the creation of new classes based on existing ones, enabling code reuse and promoting modularity.
• Polymorphism allows objects of different classes to be treated interchangeably, providing flexibility and extensibility.
• Abstraction allows developers to focus on the essential features of objects while hiding unnecessary details.

Overall, OOP is widely used in the development of software systems as it promotes code reusability, modularity, and maintainability.”

20. You are given two ListNodes of a doubly linked list. Write a function pop_tail that removes the tail of the linked list in O(1) time. Return the head and tail of the linked list as a list. If the linked list is empty after removal, return None.

This question will also test your understanding of data structures, but it will focus on the linked list. It will also assess your skill in developing an algorithm with the simplest time and space complexity.

How to Answer

Develop a function that removes the tail of a doubly linked list in constant time (O(1)). This typically involves updating the pointers of the tail node and its previous node to remove the tail node from the list. Be sure the function handles edge cases such as empty lists and updates the head and tail pointers appropriately.

Example

“To remove the tail of a doubly linked list in constant time, I would implement a function named pop_tail that updates the pointers of the tail node and its previous node. Here’s how I would approach it:

• If the list is empty or consists of only one node, I would return None, as there is no tail to remove.
• Otherwise, I would update the previous node’s next pointer to None, effectively removing the tail node from the list.
• I would update the tail pointer to point to the previous node, making it the new tail of the list.
• Finally, I would return the head and tail nodes of the modified list as a list.

Here’s a Python implementation of the function:”

class ListNode:
    def __init__(self, value):
        self.value = value
        self.next = None
        self.prev = None

def pop_tail(head: ListNode, tail: ListNode) -> [ListNode, ListNode]:
    if not head or head == tail:
        return None
    
    prev = tail.prev
    prev.next = None
    tail.prev = None
    
    return [head, prev]

head = ListNode