AVIS Enertech Private Limited Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Medium

This round had 3 coding questions of Medium to Hard level of difficulty.

Q1. 
Balanced Parentheses Combinations
Given an integer N representing the number of pairs of parentheses, find all the possible combinations of balanced parentheses using the given number of pairs.
Explanati...read more
Ans. 
Generate all possible combinations of balanced parentheses for a given number of pairs.
• Use recursion to generate all possible combinations of balanced parentheses.

• Keep track of the number of open and close parentheses used in each combination.

• Return the valid combinations as an array of strings.
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Q2. 
Trapping Rain Water Problem Statement
You are given a long type array/list ARR of size N, representing an elevation map. The value ARR[i] denotes the elevation of the ith bar. Your task is to determine th...read more
Ans. 
Calculate the total amount of rainwater that can be trapped between given elevations in an array.
• Iterate through the array and calculate the maximum height on the left and right of each bar.

• Calculate the amount of water that can be trapped at each bar by taking the minimum of the maximum heights on the left and right.

• Sum up the trapped water at each bar to get the total trapped water for the entire array.
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Q3. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. 
Find the minimum time required to rot all fresh oranges adjacent to rotten oranges.
• Create a queue to store the coordinates of rotten oranges and perform BFS to rot adjacent fresh oranges.

• Track the time taken to rot all fresh oranges and return -1 if not all fresh oranges can be rotten.

• Update the grid with the new state of oranges after each second.

• Handle edge cases such as empty grid or no fresh oranges present.

• Example...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This was a standard DS/Algo round where I was given 2 questions to solve under 60 minutes. I was able to come up with the optimal approach for both the questions and then at the end of the interview I was also asked the famous Die Hard Water Puzzle.

Q1. 
Queue Using Stacks Implementation
Design a queue data structure following the FIFO (First In First Out) principle using only stack instances.
Explanation:
Your task is to complete predefined functions t...read more
Ans. 
Implement a queue using stacks following FIFO principle.
• Use two stacks to simulate a queue.

• For enQueue operation, push elements onto stack1.

• For deQueue operation, if stack2 is empty, pop all elements from stack1 and push onto stack2, then pop from stack2.

• For peek operation, if stack2 is empty, pop all elements from stack1 and push onto stack2, then return top of stack2.

• For isEmpty operation, check if both stack1 and st...read more
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Q2. 
Merge Intervals Problem Statement
You are provided with 'N' intervals, each containing two integers denoting the start time and end time of the interval.
Your task is to merge all overlapping intervals a...read more
Ans. 
Merge overlapping intervals and return sorted list of merged intervals by start time.
• Sort the intervals based on start time.

• Iterate through intervals and merge overlapping ones.

• Return the merged intervals in sorted order.
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Q3. You have a 3-liter jar and a 5-liter jar. How can you measure exactly 4 liters using these two jars?
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 2 coding questions - first one related to Binary Tree and the second one was a simple question from Bit Manipulation. This was followed by some questions from OOPS.

Q1. 
Binary Tree Diameter Problem Statement
You are given a Binary Tree, and you need to determine the length of the diameter of the tree.
The diameter of a binary tree is the length of the longest path betwe...read more
Ans. 
The task is to find the diameter of a binary tree, which is the length of the longest path between any two end nodes in the tree.
• Traverse the tree to find the longest path between two nodes.

• Keep track of the maximum diameter found during traversal.

• The diameter may not necessarily pass through the root node.

• Consider both left and right subtrees while calculating the diameter.

• Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1
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Q2. 
Power of 2 Problem Statement
Determine if it is possible to reorder the digits of a given integer 'N' such that the resulting number is a power of two. The leading digit must not be zero.
Input:
The fir...read more
Ans. 
The problem involves determining if it is possible to reorder the digits of a given integer to form a power of 2.
• Iterate through all possible permutations of the digits of the given integer.

• Check if any of the permutations form a power of 2.

• Return 1 if a valid permutation is found, else return 0.
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Q3. What are some advantages of using Object-Oriented Programming (OOP)?
Ans. 
Advantages of OOP include code reusability, modularity, and easier maintenance.
• Code reusability: Objects can be reused in different parts of the program, reducing redundancy.

• Modularity: OOP allows for breaking down complex problems into smaller, more manageable parts.

• Easier maintenance: Changes to one part of the codebase do not necessarily affect other parts, making maintenance easier.

• Encapsulation: Data hiding and ab...read more
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Q4. What are access specifiers and what is their significance in Object-Oriented Programming?
Ans. 
Access specifiers define the level of access to class members in Object-Oriented Programming.
• Access specifiers include public, private, protected, and default

• Public members are accessible from outside the class

• Private members are only accessible within the class

• Protected members are accessible within the class and its subclasses

• Default access is when no access specifier is specified
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Round duration - 30 Minutes
Round difficulty - Easy

This was my last round and I hoped it to go good just like the other rounds. The interviewer was very straight to point
and professional. The interview lasted for 30 minutes.

Q1. Why should we hire you?
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Round duration - 60 Minutes
Round difficulty - Medium

This round started with some questions from Programmable Logic Controllers or PLC followed by some basic questions from Intel 8051 Microcontroller.

Q1. What are the general functions of a Programmable Logic Controller (PLC)?
Ans. 
PLCs are used to control machinery and automate processes in industrial settings.
• Monitoring inputs from sensors

• Executing control algorithms

• Communicating with other devices

• Logging data for analysis

• Implementing safety functions

• Examples: controlling a conveyor belt, regulating temperature in a furnace
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Q2. Can you describe the basic elements in Ladder logic programming?
Ans. 
Ladder logic programming is a graphical programming language used for PLCs, with basic elements like contacts, coils, timers, and counters.
• Ladder logic consists of rungs, which are made up of inputs (contacts) and outputs (coils).

• Contacts represent conditions that must be met for the output to be energized.

• Coils are outputs that are energized when the conditions of the contacts are met.

• Timers and counters are used to c...read more
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Q3. What are the different types of PLC inputs and outputs?
Ans. 
PLC inputs and outputs include digital inputs, digital outputs, analog inputs, and analog outputs.
• Digital inputs: used for receiving binary signals (on/off, high/low). Examples: push buttons, limit switches.

• Digital outputs: used for sending binary signals. Examples: relays, solenoids.

• Analog inputs: used for receiving continuous signals. Examples: temperature sensors, pressure transducers.

• Analog outputs: used for sendin...read more
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Q4. What are the advantages and disadvantages of the S7 controller?
Ans. 
The S7 controller offers high performance and flexibility but can be complex to program and expensive.
• Advantages: high performance, flexibility, scalability

• Disadvantages: complexity in programming, expensive

• Example: S7-1200 offers fast processing speeds and can be easily expanded with additional modules

• Example: Programming for S7 controllers may require specialized training and expertise
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Q5. Can you explain the time stamp available in the S7-200 PLC?
Ans. 
The time stamp in S7-200 PLC is used to record the time when a specific event occurs.
• Time stamp is a feature in S7-200 PLC that records the time when a specific event happens.

• It helps in tracking the sequence of events and troubleshooting issues.

• Time stamp can be used to monitor the performance of the PLC system.

• Example: A time stamp can be recorded when a sensor detects a change in temperature.

• Example: Time stamp can ...read more
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Q6. Could you explain Jnc in the context of microcontrollers?
Ans. 
Jnc stands for Jump and Call in the context of microcontrollers.
• Jnc is an instruction used in microcontrollers to jump to a specified address if the carry flag is not set.

• It is commonly used in conditional branching operations in microcontroller programming.

• For example, in 8051 microcontroller assembly language, the instruction JNC label will jump to the specified label if the carry flag is not set.
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Q7. What are the types of interrupts in the Intel 8051 microcontroller?
Ans. 
The types of interrupts in the Intel 8051 microcontroller include external hardware interrupts, timer interrupts, and serial communication interrupts.
• External hardware interrupts are triggered by external devices connected to the microcontroller.

• Timer interrupts are generated by the internal timers of the microcontroller.

• Serial communication interrupts occur when data is received or transmitted through the serial port.

• ...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This round was heavily inclined towards Operating System and Computer Networks and the interviewer asked questions revolving around the fundamentals of the subject.

Q1. What is a bootstrap program in an operating system?
Ans. 
A bootstrap program is a small program that initializes the operating system on a computer.
• Bootstrap program is stored in ROM or EEPROM and is executed when the computer is powered on.

• It loads the operating system kernel into memory and starts its execution.

• Bootstrap program is responsible for setting up the initial state of the operating system.

• Examples include BIOS (Basic Input/Output System) in PCs and UEFI (Unified
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Q2. Can you explain demand paging?
Ans. 
Demand paging is a memory management scheme where pages are only brought into memory when they are demanded by the program.
• Pages are loaded into memory only when needed

• Helps in reducing the amount of physical memory required

• Improves overall system performance by allowing more processes to run simultaneously

• Commonly used in virtual memory systems
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Q3. Can you explain any 5 essential UNIX commands?
Ans. 
Five essential UNIX commands are ls, cd, pwd, mkdir, and rm.
• ls - list directory contents

• cd - change directory

• pwd - print working directory

• mkdir - make directory

• rm - remove files or directories
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Q4. What are the different types of VPN?
Ans. 
Different types of VPN include remote access VPN, site-to-site VPN, and client-to-site VPN.
• Remote access VPN allows individual users to connect to a private network from a remote location.

• Site-to-site VPN connects entire networks together over the internet.

• Client-to-site VPN allows individual devices to connect to a private network.

• Examples include OpenVPN, IPsec, and SSL VPN.
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Q5. Can you describe the OSI Reference Model?
Ans. 
The OSI Reference Model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven layers.
• The OSI Reference Model stands for Open Systems Interconnection Reference Model.

• It consists of seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer has specific functions and communicates with the adjacent layers for data trans...read more
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Q6. Can you explain the TCP and UDP protocols?
Ans. 
TCP is a connection-oriented protocol that ensures reliable data delivery, while UDP is a connectionless protocol that focuses on speed.
• TCP stands for Transmission Control Protocol and is used for reliable data transmission.

• TCP establishes a connection between sender and receiver before data transfer.

• TCP uses sequencing and acknowledgment to ensure data integrity.

• UDP stands for User Datagram Protocol and is used for fa...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my
role.

Q1. What is something about you that is not included in your resume?
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