Comcast India Engineering Center Devops Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Medium

The interviewer was really cool. He realized that I mostly work on java applications so he chose to ask me stuff related to that. He didn't want me to know the answer well but just wanted me to approach to it, maybe think more. He went through my resume back and forth and asked mostly about all my projects and their logic and how could I take them to the next level.
Tips: Be confident. Its okay not to know any answer, just try giving it a shot in the approach.

Q1. What is the difference between an abstract class and an interface in Java?
Ans. 
Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructors, member variables, and methods with implementation.

• Interface can only have abstract methods and constants.

• A class can implement multiple interfaces but can only extend one abstract class.

• Example: Abstract class - Animal with abstract method 'eat', Interface - Flyable with m...read more
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Q2. What is the difference between 'final', 'finally', and 'finalize' in Java?
Ans. 
final is a keyword used to declare constants, finally is a block used in exception handling, and finalize is a method used for cleanup.
• final is a keyword used to declare constants in Java, meaning the value cannot be changed once assigned. Example: final int x = 10;

• finally is a block used in exception handling to ensure a piece of code is always executed, whether an exception is thrown or not. Example: try { // code } ...read more
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Q3. What is the difference between the private and final access modifiers in Java?
Ans. 
Private restricts access to the class itself, while final prevents inheritance and method overriding.
• Private access modifier restricts access to the class itself, while final access modifier prevents inheritance and method overriding.

• Private members are only accessible within the same class, while final classes cannot be extended and final methods cannot be overridden.

• Example: private int num; - num can only be accesse...read more
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Q4. What are the steps for establishing a JDBC connection?
Ans. 
Establishing a JDBC connection involves loading the driver, creating a connection, creating a statement, executing queries, and handling exceptions.
• Load the JDBC driver using Class.forName() method

• Create a connection using DriverManager.getConnection() method

• Create a statement using connection.createStatement() method

• Execute queries using statement.executeQuery() method

• Handle exceptions using try-catch blocks
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Q5. What is JSON?
Ans. 
JSON is a lightweight data interchange format used to store and transmit data between a server and a web application.
• JSON stands for JavaScript Object Notation.

• It is easy for humans to read and write, and easy for machines to parse and generate.

• JSON is language-independent and can be used with any programming language.

• Example: {"name": "John", "age": 30}

• Example: [{"name": "Alice", "age": 25}, {"name": "Bob", "age": 35}...read more
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Q6. What do you know about garbage collection in Java?
Ans. 
Garbage collection in Java is the process of automatically managing memory by deallocating objects that are no longer needed.
• Garbage collection helps in preventing memory leaks by reclaiming memory used by objects that are no longer referenced.

• Java uses a garbage collector to automatically manage memory, unlike languages like C++ where memory management is manual.

• Garbage collection in Java can be triggered by calling S...read more
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Round duration - 30 minutes
Round difficulty - Easy

I wouldn't say it went great but it was fine. I did not think I would clear it as for most of the questions the interviewer seemed disappointed and wanted more out of me.

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Level Order Traversal Problem Statement
Given a binary tree of integers, return the level order traversal of the binary tree.
Input:
The first line contains an integer 'T', representing the number of te...read more
Ans. 
Return the level order traversal of a binary tree given in level order with null nodes represented by -1.
• Create a queue to store nodes for level order traversal

• Start with the root node and add it to the queue

• While the queue is not empty, dequeue a node, print its value, and enqueue its children

• Repeat until all nodes are traversed in level order
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Round duration - 45 minutes
Round difficulty - Easy

Q1. What is a deadlock in DBMS, and can you explain the concepts of join and query?
Ans. 
A deadlock in DBMS occurs when two or more transactions are waiting for each other to release locks, causing them to be stuck indefinitely.
• Deadlock is a situation where two or more transactions are unable to proceed because each is waiting for the other to release locks.

• To prevent deadlocks, DBMS uses techniques like deadlock detection and prevention algorithms.

• Joins in DBMS are used to combine rows from two or more ta...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. Design a system for Twitter, outlining the key components and architecture involved.
Ans. 
Design a system for Twitter
• Key components: user profiles, tweets, hashtags, timelines

• Architecture: microservices, load balancers, databases, caching

• Scalability: sharding, replication, CDN

• Real-time processing: streaming APIs, push notifications
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Maximum Subarray Sum Queries
You are provided with an array of ‘N’ integers and ‘Q’ queries. Each query requires calculating the maximum subarray sum in a specified range of the array.
Input:
The first ...read more
Ans. 
Implement a function to calculate maximum subarray sum queries in a given range of an array.
• Iterate through each query and calculate the maximum subarray sum within the specified range using Kadane's algorithm.

• Keep track of the maximum sum found so far and update it as needed.

• Return the maximum subarray sum for each query in the test case.
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an integer array containing only 0s, 1s, and 2s in linear time complexity.
• Use a single scan over the array to sort it in-place.

• Maintain three pointers for 0s, 1s, and 2s and swap elements accordingly.

• Example: Input: [0, 2, 1, 2, 0], Output: [0, 0, 1, 2, 2]
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Round duration - 20 Minutes
Round difficulty - Medium