WatchGuard Technologies Senior Software Engineer Interview Questions and Answers

Q1. Data structures, Algorithm
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Basic question asked

Q1. Computer networking based question
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Q2. Dsa question based on graph and dp
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Q3. Based on operating system
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Q4. Function of oops
Ans. 
Object-oriented programming paradigm that focuses on objects and classes for code organization and reusability.
• Encapsulation: bundling data and methods that operate on the data into a single unit (object)

• Inheritance: ability of a class to inherit properties and behavior from another class

• Polymorphism: ability to present the same interface for different data types
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Q1. Behavior question asked
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Round duration - 60 minutes
Round difficulty - Medium

The test was in the evening which was not too late. It was conducted on Hackerrank which is a very common platform and was hence familiar. There were 26 questions:
Q1: Coding Question
3 languages were allowed: c, java8, python3
Q2 - Q26: Multiple Choice Questions

Q1. 
Intersection of Linked List Problem
You are provided with two singly linked lists containing integers, where both lists converge at some node belonging to a third linked list.
Your task is to determine t...read more
Ans. 
Find the node where two linked lists merge, return -1 if no merging occurs.
• Traverse both lists to find the lengths and the last nodes

• Align the starting points of both lists by moving the longer list's pointer ahead by the difference in lengths

• Traverse both lists simultaneously until a common node is found, which is the merging point
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Round duration - 70 Minutes
Round difficulty - Medium

This was an Online Coding+MCQ round where we had a total of 50 MCQ questions and 1 coding problem. The coding problem was of easy to medium level but was a bit implementation heavy.

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Implement a doubly linked list to maintain the order of recently used keys.

• Use a hashmap to store key-value pairs for quick access.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the position of a key in the linked list whenever it is accessed or updated.

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

This round had 1 coding question in which I was first required to explain my approach and then discuss the time and space complexities. After this , some basic questions from OOPS and Java were asked.

Q1. 
Detect and Remove Loop in Linked List
For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.
Expected Complexity:
A...read more
Ans. 
Detect and remove loop in a singly linked list in place with O(n) time complexity and O(1) space complexity.
• Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

• Once the loop is detected, use two pointers to find the start of the loop.

• Adjust the pointers to remove the loop and return the modified linked list.
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Q2. What is the difference between ArrayList and LinkedList in Java?
Ans. 
ArrayList is implemented using a dynamic array while LinkedList is implemented using a doubly linked list.
• ArrayList provides fast random access but slow insertion and deletion operations.

• LinkedList provides fast insertion and deletion operations but slow random access.

• Example: ArrayList is suitable for scenarios where frequent access and traversal of elements is required, while LinkedList is suitable for scenarios wher...read more
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Q3. What is the difference between abstraction and inheritance?
Ans. 
Abstraction focuses on hiding implementation details, while inheritance allows a class to inherit properties and behavior from another class.
• Abstraction is the concept of hiding the complex implementation details and showing only the necessary features of an object.

• Inheritance is a mechanism where a new class inherits properties and behavior from an existing class.

• Abstraction is achieved through interfaces and abstract...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round had questions from OS and OOPS. The interviewer also tested my problem solving skills by asking me some puzzles in the end.

Q1. Can you explain piping in Unix/Linux?
Ans. 
Piping in Unix/Linux allows the output of one command to be used as the input for another command.
• Piping is done using the | symbol

• Multiple commands can be piped together

• Piping allows for the creation of complex command chains

• Example: ls -l | grep txt
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Q2. What is a static variable in C?
Ans. 
A static variable in C is a variable that retains its value between function calls.
• Static variables are declared using the 'static' keyword.

• They are initialized only once and retain their value throughout the program's execution.

• Static variables have a default value of 0 if not explicitly initialized.

• They are stored in the data segment of the program's memory.

• Example: static int count = 0; declares a static variable 'c
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Q3. How can you measure exactly 4 liters of water using only a 3-liter can and a 5-liter can?
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Round duration - 60 Minutes
Round difficulty - Medium

This was an Online Coding+MCQ round where we had a total of 25 MCQ questions and 1 coding problem. The coding problem was of easy to medium level and anyone with a decent knowledge of DSA could pass the coding problem.

Q1. 
Rat In a Maze Problem Statement
Given a N * N maze with a rat placed at position MAZE[0][0], find and print all possible paths for the rat to reach its destination at MAZE[N-1][N-1]. The rat is allowed to...read more
Ans. 
Find all possible paths for a rat in a maze to reach its destination.
• Use backtracking to explore all possible paths in the maze.

• Mark visited cells and backtrack when reaching dead ends.

• Print the path when reaching the destination cell.

• Consider all possible movements: left, right, up, and down.

• Ensure the rat can only move through cells marked as 1.
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Round duration - 60 Minutes
Round difficulty - Medium

The interviewer asked 1 coding problem related to Dynamic Programming in this round and then the rest of the questions were preety much revolving around Computer Networks.

Q1. 
Ways To Make Coin Change
Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make...read more
Ans. 
The task is to find the total number of ways to make change for a specified value using given denominations.
• Use dynamic programming to solve this problem efficiently.

• Create a 1D array to store the number of ways to make change for each value from 0 to the target value.

• Iterate through the denominations and update the array based on the current denomination.

• The final answer will be the value at the target index of the ar
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Q2. What is the difference between IPv4 and IPv6?
Ans. 
IPv6 has a larger address space, improved security features, and better support for mobile devices compared to IPv4.
• IPv4 uses 32-bit addresses while IPv6 uses 128-bit addresses.

• IPv4 supports around 4.3 billion unique addresses, whereas IPv6 supports 340 undecillion unique addresses.

• IPv6 has built-in security features like IPsec, while IPv4 requires additional security protocols.

• IPv6 has better support for mobile device...read more
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Q3. 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.

• The model help...read more
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Round duration - 60 minutes
Round difficulty - Medium

This round had 1 question related to Binary Tree Traversal followed by some core concepts related to Operating Systems. This round ended with the interviewer asking me the famous 2 wire burning puzzle.

Q1. 
Spiral Order Traversal of a Binary Tree
Given a binary tree with N nodes, your task is to output the Spiral Order traversal of the binary tree.
Input:
The input consists of a single line containing elem...read more
Ans. 
Implement a function to return the spiral order traversal of a binary tree.
• Traverse the binary tree in a spiral order, alternating between left to right and right to left at each level

• Use a queue to keep track of nodes at each level and a flag to switch direction

• Return the list of nodes in spiral order traversal
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Q2. What is memory protection in operating systems?
Ans. 
Memory protection in operating systems is a mechanism to prevent a process from accessing memory that has not been allocated to it.
• Memory protection prevents a process from accessing memory locations outside its allocated space.

• It helps in preventing one process from interfering with the memory of another process.

• Operating systems use techniques like virtual memory and access control lists to implement memory protectio...read more
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Q3. You have two wires of different lengths that take different times to burn. How can you measure a specific amount of time using these two wires?
Ans. 
Use two wires of different lengths to measure a specific amount of time by burning them simultaneously.
• Burn both wires at the same time, one wire will finish burning before the other

• Measure the time it takes for the first wire to burn completely

• Use this time as a reference to measure the specific amount of time by burning the second wire
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Round duration - 90 minutes
Round difficulty - Medium

25 MCQS: Based on OS, CN, and aptitude.
1 Coding questions: Medium. I was able to solve it. The question was based on string and hashmap

Q1. 
Word Break Problem Statement
You are given a list of N strings called A. Your task is to determine whether you can form a given target string by combining one or more strings from A.
The strings from A c...read more
Ans. 
Given a list of strings, determine if a target string can be formed by combining one or more strings from the list.
• Iterate through all possible combinations of strings from the list to check if they form the target string.

• Use recursion to try different combinations of strings.

• Optimize the solution by using memoization to store intermediate results.

• Handle edge cases like empty input or target string.
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Round duration - 60 Minutes
Round difficulty - Easy

This was the initial round consisting of some aptitude questions,technical multiple choice questions and one coding question.
The Multiple Choice Questions were pretty straight forward.

Q1. 
Snake and Ladder Problem Statement
Given a 'Snake and Ladder' board with N rows and N columns, where positions are numbered from 1 to (N*N) starting from the bottom left, alternating direction each row, f...read more
Ans. 
Find the minimum number of dice throws required to reach the last cell on a 'Snake and Ladder' board.
• Start from the bottom left cell and move according to dice outcomes (1-6).

• Utilize snakes and ladders to reach the last cell faster.

• Keep track of the minimum number of throws required to reach the last cell.

• If unreachable, return -1 as output.
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Round duration - 45 Minutes
Round difficulty - Medium

I had two interviewers in this round.Some Problem solving questions were asked in this round.

Q1. 
Anagram Pairs Verification Problem
Your task is to determine if two given strings are anagrams of each other. Two strings are considered anagrams if you can rearrange the letters of one string to form the...read more
Ans. 
Check if two strings are anagrams of each other by comparing their sorted characters.
• Sort the characters of both strings and compare them.

• Use a dictionary to count the frequency of characters in each string and compare the dictionaries.

• Ensure both strings have the same length before proceeding with comparison.

• Example: For input 'spar' and 'rasp', after sorting both strings, they become 'aprs' which are equal, so return
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Q2. Can you explain all the main Object Oriented Programming concepts?
Ans. 
Object Oriented Programming concepts include encapsulation, inheritance, polymorphism, and abstraction.
• Encapsulation: Bundling data and methods that operate on the data into a single unit (class). Example: Class Car with properties like color and methods like drive().

• Inheritance: Creating new classes based on existing classes, inheriting their attributes and methods. Example: Class SUV inheriting from class Car.

• Polymor...read more
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Q3. Can you explain one of your projects?
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Round duration - 45 Minutes
Round difficulty - Easy

Number Of Interviewers : 2
I was asked two problem solving questions and I was asked to explain my projects.

Round duration - 60 minutes
Round difficulty - Hard

There were 2 coding questions and 15 MCQs (related to OOPs, OS, DBMS, CN, DSA, and Aptitude).

Q1. 
Apple Pickup Problem Statement
Alice has a garden represented as a ‘N’ * ‘N’ grid called ‘MATRIX’. She wants to collect apples following these rules:
• 1 -> Alice can pick an apple from this cell and ...read more
Ans. 
The problem involves finding the maximum number of apples Alice can collect in a grid while following specific rules.
• Create a recursive function to explore all possible paths from the starting point to the ending point while keeping track of the collected apples.

• Consider the constraints and optimize the solution to avoid unnecessary computations.

• Use dynamic programming to store and reuse the results of subproblems to i...read more
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Q2. 
Implement Stack with Linked List
Your task is to implement a Stack data structure using a Singly Linked List.
Explanation:
Create a class named Stack which supports the following operations, each in O(1...read more
Ans. 
Implement a Stack data structure using a Singly Linked List with operations in O(1) time.
• Create a class named Stack with getSize, isEmpty, push, pop, and getTop methods.

• Use a Singly Linked List to store the elements of the stack.

• Ensure each operation runs in constant time complexity.

• Handle edge cases like empty stack appropriately.

• Example: If input is '5 3 10 5 1 2 4', the output should be '10 1 false'.
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Round duration - 40 minutes
Round difficulty - Medium

It was a technical interview round where I was asked questions based on DSA.

Q1. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
Detect if a singly linked list forms a cycle by checking if a node's next points back to a previous node.
• Use Floyd's Tortoise and Hare algorithm to detect a cycle in the linked list.

• Initialize two pointers, slow and fast, and move them at different speeds to detect a cycle.

• If there is a cycle, the fast pointer will eventually catch up to the slow pointer.

• If the fast pointer reaches the end of the list (null), there is
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Q2. 
Find the Lone Set Bit
Your task is to identify the position of the only '1' bit in the binary representation of a given non-negative integer N. The representation contains exactly one '1' and the rest are...read more
Ans. 
Find the position of the lone '1' bit in the binary representation of a given non-negative integer.
• Iterate through the bits of the integer to find the position of the lone '1'.

• Use bitwise operations to check if there is exactly one '1' bit in the binary representation.

• Return the position of the lone '1' or -1 if there isn't exactly one '1'.
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Round duration - 30 minutes
Round difficulty - Medium

It was a technical interview round where I was asked questions based on DSA, OS, and Networking.

Q1. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. 
Given an array of integers and a target, find all pairs of elements that add up to the target.
• Iterate through the array and for each element, check if the target minus the element exists in a hash set.

• If it exists, add the pair to the result. If not, add the element to the hash set.

• Handle cases where the same element is used twice to form a pair.

• Return (-1, -1) if no pair is found.
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Q2. What is priority inversion?
Ans. 
Priority inversion is a scenario in scheduling where a lower priority task holds a resource needed by a higher priority task, causing the higher priority task to wait.
• Occurs when a low priority task locks a resource needed by a high priority task

• Results in the high priority task being blocked and unable to proceed

• Can lead to delays in critical tasks and impact system performance

• Commonly addressed through priority inher
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Q3. What happens when you boot your system?
Ans. 
During system boot, the BIOS performs Power-On Self Test (POST), loads the operating system, and initializes hardware components.
• BIOS (Basic Input/Output System) performs Power-On Self Test (POST) to check hardware components

• BIOS loads the bootloader from the boot device (e.g. hard drive, SSD)

• Bootloader loads the operating system kernel into memory

• Operating system initializes hardware components and starts system servi...read more
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Q4. What is an IP address and how many bits are required to represent it?
Ans. 
An IP address is a unique numerical label assigned to each device connected to a computer network, typically represented by 32 bits.
• An IP address is used to identify and locate devices on a network.

• It consists of four sets of numbers separated by periods, such as 192.168.1.1.

• IPv4 addresses are 32 bits long, while IPv6 addresses are 128 bits long.
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Round duration - 10 minutes
Round difficulty - Easy

This was an HR round. The interviewer asked me some questions.
Finally, she asked if I had any questions for her.