Epsilon Lead Software Engineer Interview Questions and Answers

Round duration - 90 Minutes
Round difficulty - Hard

The test was at 6 pm with cam on and in fullscreen mode.

Q1. 
Interleaving Two Strings Problem Statement
You are given three strings 'A', 'B', and 'C'. Determine if 'C' is formed by interleaving 'A' and 'B'.
String 'C' is an interleaving of 'A' and 'B' if the lengt...read more
Ans. 
The problem involves determining if a string 'C' is formed by interleaving two given strings 'A' and 'B'.
• Check if the length of 'C' is equal to the sum of the lengths of 'A' and 'B'.

• Verify if all characters of 'A' and 'B' exist in 'C' while maintaining their order.

• Return 'True' if 'C' is an interleaving of 'A' and 'B', otherwise return 'False'.
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Q2. 
Construct Binary Tree from Inorder and Postorder Traversal
Given two lists representing the inorder and postorder traversal of a binary tree of integer type with 'N' nodes, construct the binary tree and r...read more
Ans. 
Construct a binary tree from inorder and postorder traversal lists and return its root.
• Create a map to store the indices of elements in the inorder traversal list for quick access during tree construction.

• Use the postorder list to determine the root of the tree and recursively build left and right subtrees.

• Construct the tree by recursively dividing the inorder list based on the root index in postorder list.

• Return the r...read more
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Round duration - 45 Minutes
Round difficulty - Easy

At 10:00 AM. Interviewer was very friendly and young but his cam was off.

Q1. 
Find Paths in Binary Tree
Kevin has sketched a series of integers, forming a diagram that represents a binary tree. Challenged by a friend, Kevin needs to find all paths from the root to the leaf where th...read more
Ans. 
Find all root-to-leaf paths in a binary tree that sum to a given number K.
• Use Depth-First Search (DFS) to traverse the tree.

• Keep track of the current path and its sum as you traverse.

• When a leaf node is reached, check if the sum equals K.

• If it does, store the path as a valid result.

• Example: For tree [5, 6, 4] and K=15, path [5, 6, 4] is valid.
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Round duration - 45 Minutes
Round difficulty - Easy

It was held at 4 p.m. The interviewer was senior compared to the one in the previous round. Also, his cam was also on, but he wasn't speaking much and neither giving any expressions.

Q1. 
Boxes of Power Problem Statement
Given a set of boxes represented by an array gainPower, where each box has a certain power value, along with an initial power value 'power', your task is to maximize the t...read more
Ans. 
Maximize total score by selecting boxes optimally based on power values and operations.
• Iterate through the boxes and perform operations based on power values and current score

• Keep track of power, score, and selected boxes to maximize total score

• Example: For input [3, 50, [20, 30, 40]], select boxes with power 20 and 30 to get a score of 2
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Q1. Python, sql, etl, cloud, web tool
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Q1. Functional question and write some sql basic query
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Q1. Basic question on project
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Q1. Salary negotiation and check behaviour qiestion
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Q1. Basic JavaScript and React.js questions
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Q2. Questions on functions, hooks and DOM
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Q3. Questions on SSR
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Q4. Questions on strings and arrays
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Api related questions

Q1. What is Indexing in Mysql
Ans. 
Indexing in MySQL is a technique to improve the performance of database queries by creating a data structure that allows for faster data retrieval.
• Indexes are created on one or more columns of a table.

• They help in speeding up the search, sorting, and joining of data.

• Indexes can be created using different algorithms like B-tree, hash, or bitmap.

• Using indexes appropriately can significantly enhance query performance.

• Exam...read more
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Q2. Opps concepts in php
Ans. 
Object-oriented programming concepts in PHP
• Encapsulation: bundling data and methods together in a class

• Inheritance: creating new classes based on existing ones

• Polymorphism: using a single interface to represent different types

• Abstraction: hiding unnecessary details and exposing only essential features

• Class: blueprint for creating objects

• Object: instance of a class

• Method: function defined inside a class

• Property: variabl...read more
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Q1. Explain oops concepts, difference b/w abstraction and interface,MVC architecture,stored procedure,joins
Ans. 
OOPs concepts, abstraction vs interface, MVC architecture, stored procedures, joins
• OOPs concepts include inheritance, polymorphism, encapsulation, and abstraction

• Abstraction is hiding the implementation details while interface is a contract that defines the methods that a class must implement

• MVC architecture separates the application into Model, View, and Controller components for better organization and maintenance

• Sto...read more
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SQL queries, ddl,dml TCL commands, primary key and foreign key differences,what is composite key,hash table in c#,generics in c#.

Q1. Salary discussion,
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Q1. Pivot columns in sql
Ans. 
Pivoting columns in SQL involves transforming rows into columns to display data in a different format.
• Use the PIVOT keyword in SQL to pivot columns

• Specify the columns to pivot on and the values to display in the new columns

• Aggregate functions like SUM, AVG, COUNT can be used with PIVOT

• Example: SELECT * FROM table_name PIVOT (SUM(value_column) FOR pivot_column IN ('value1', 'value2', 'value3'))
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Q2. Slow changing dimensions
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Q3. Dynamic rankx top 3
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Q4. Field parameters
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Q5. Stored procedures
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