WebEngage Android Developer Interview Questions and Answers

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

It was online 60min test.

It was offline 30 min test.

Q1. Oops,dbms,css,html,dsa,java.
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Q2. It was very friendly .
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Q1. What are the 4 principles of oops?
Ans. 
The 4 principles of OOP are Inheritance, Encapsulation, Abstraction, and Polymorphism.
• Inheritance allows a class to inherit properties and behavior from another class.

• Encapsulation restricts access to certain components within a class, protecting the data.

• Abstraction hides complex implementation details and only shows the necessary features.

• Polymorphism allows objects to be treated as instances of their parent class.
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Q2. What is the difference between string buffer and string builder?
Ans. 
String buffer is synchronized and thread-safe, while string builder is not synchronized and faster.
• String buffer is synchronized, making it thread-safe for use in multi-threaded environments.

• String builder is not synchronized, providing better performance in single-threaded applications.

• String builder is faster than string buffer due to lack of synchronization overhead.

• Example: StringBuffer sb = new StringBuffer(); Str
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Q3. Why strings are immutable?
Ans. 
Strings are immutable in order to ensure data integrity and security.
• Immutable strings prevent accidental data modification, ensuring data integrity.

• Immutable strings enhance security by preventing unauthorized access or tampering.

• Immutable strings allow for more efficient memory management and optimization.

• Example: 'Hello' cannot be changed to 'Hella' directly, a new string must be created.
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Q4. What are the different types of exception in java?
Ans. 
There are two types of exceptions in Java: checked exceptions and unchecked exceptions.
• Checked exceptions are checked at compile time and must be handled using try-catch or throws keyword.

• Unchecked exceptions are not checked at compile time and include RuntimeException and its subclasses.

• Examples of checked exceptions include IOException, SQLException, and ClassNotFoundException.

• Examples of unchecked exceptions include...read more
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Q5. Explain linear search algorithm.
Ans. 
Linear search is a simple searching algorithm that sequentially checks each element in a list until a match is found.
• Iterate through each element in the list

• Compare the current element with the target value

• Return the index if a match is found, otherwise return -1
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Q6. Difference between JDK jvm and jre
Ans. 
JDK includes JRE and development tools, while JRE includes only the Java Runtime Environment.
• JDK stands for Java Development Kit, which includes JRE and development tools like compilers and debuggers.

• JRE stands for Java Runtime Environment, which includes JVM and libraries necessary to run Java applications.

• JVM stands for Java Virtual Machine, which is responsible for executing Java bytecode.

• JDK is used for developing ...read more
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25 MCQ questions online with time limit

Create webapp . Frontend, Backend , data encryption

Easy to medium
profit and loss questions
Permutation and combination

Easy to medium
45 mins

Q1. Basic concept of Oops Java basic
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Q2. Constructor Overloading
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Q3. Operator overloading in Java?
Ans. 
Operator overloading allows operators to be redefined for user-defined types in Java.
• Operator overloading is not supported in Java as it can lead to ambiguity and confusion.

• Java does not allow custom operators to be defined or existing operators to be overloaded.

• Instead of operator overloading, Java provides method overloading where methods with the same name but different parameters can be defined.
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Q4. Define java and it's features
Ans. 
Java is a high-level, object-oriented programming language known for its platform independence and robust features.
• Java is platform-independent, meaning it can run on any device with a Java Virtual Machine (JVM)

• It is object-oriented, allowing for modular and reusable code

• Java is known for its robust standard library, which includes tools for networking, I/O, and more

• It supports multithreading, allowing for concurrent e...read more
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Q1. Introduction Present events
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Easy aptitude, 30 min with 20 question