F5 Networks Software Developer Interview Questions, Process, and Tips

Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions based on DSA.

Q1. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from the end to the beginning and append each character to a new string.

• Use built-in functions like reverse() or StringBuilder in languages like Python or Java for efficient reversal.

• Handle special characters and numbers along with alphabets while reversing the string.

• Ensure to consider the constraints on the number ...read more
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Q2. 
Flip Bits Problem Explanation
Given an array of integers ARR of size N, consisting of 0s and 1s, you need to select a sub-array and flip its bits. Your task is to return the maximum count of 1s that can b...read more
Ans. 
Given an array of 0s and 1s, find the maximum count of 1s by flipping a sub-array at most once.
• Iterate through the array and keep track of the maximum count of 1s obtained by flipping a sub-array.

• Consider flipping a sub-array from index i to j by changing 0s to 1s and vice versa.

• Update the maximum count of 1s if the current count is greater.

• Return the maximum count of 1s obtained after flipping a sub-array at most once
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Q3. 
Check If Preorder Traversal Is Valid
Determine whether a given array ARR of positive integers is a valid Preorder Traversal of a Binary Search Tree (BST).
A binary search tree (BST) is a tree structure w...read more
Ans. 
Check if a given array of positive integers is a valid Preorder Traversal of a Binary Search Tree (BST).
• Create a function that takes the array as input and checks if it satisfies the properties of a BST preorder traversal.

• Iterate through the array and maintain a stack to keep track of the nodes in the BST.

• Compare each element with the top of the stack to ensure it follows the BST property.

• If the array is a valid preord...read more
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Q4. 
First and Last Position of an Element in a Sorted Array
Given a sorted array/list ARR consisting of ‘N’ elements, and an integer ‘K’, your task is to find the first and last occurrence of ‘K’ in ARR.
Exp...read more
Ans. 
Find the first and last occurrence of a given element in a sorted array.
• Use binary search to find the first occurrence of the element.

• Use binary search to find the last occurrence of the element.

• Handle cases where the element is not present in the array.
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on DSA, OS, OOPS etc.

Q1. 
Intersection of Two Arrays Problem Statement
Given two arrays A and B with sizes N and M respectively, both sorted in non-decreasing order, determine their intersection.
The intersection of two arrays in...read more
Ans. 
The problem involves finding the intersection of two sorted arrays efficiently.
• Use two pointers to iterate through both arrays simultaneously.

• Compare elements at the pointers and move the pointers accordingly.

• Handle cases where elements are equal or not equal to find the intersection.

• Return the intersection as an array of common elements.
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Q2. 
Remove Duplicates From Unsorted Linked List Problem Statement
You are provided with a linked list consisting of N nodes. Your task is to remove duplicate nodes such that each element occurs only once in t...read more
Ans. 
Remove duplicates from an unsorted linked list while preserving the order of nodes.
• Iterate through the linked list while keeping track of seen elements using a hash set.

• If a duplicate element is encountered, skip it by adjusting the pointers.

• Ensure the order of nodes is preserved by only keeping the first occurrence of each element.
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Q3. What is the difference between paging and swapping in operating systems?
Ans. 
Paging is a memory management scheme that allows the operating system to store and retrieve data from secondary storage in fixed-size blocks, while swapping involves moving entire processes between main memory and disk.
• Paging involves dividing physical memory into fixed-size blocks called pages, while swapping involves moving entire processes between main memory and disk.

• Paging allows for more efficient use of physical...read more
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Q4. Can you provide an example of a deadlock in operating systems?
Ans. 
A deadlock in operating systems occurs when two or more processes are unable to proceed because each is waiting for the other to release a resource.
• Deadlock involves a circular wait, where each process is waiting for a resource held by another process in the cycle.

• Four necessary conditions for deadlock are mutual exclusion, hold and wait, no preemption, and circular wait.

• Example: Process A holds Resource 1 and waits fo...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions on DSA, OOPS and Puzzles.

Q1. 
Segregate Odd-Even Problem Statement
In a wedding ceremony at NinjaLand, attendees are blindfolded. People from the bride’s side hold odd numbers, while people from the groom’s side hold even numbers. For...read more
Ans. 
Rearrange a linked list such that odd numbers appear before even numbers while preserving the order of appearance.
• Iterate through the linked list and maintain two separate lists for odd and even numbers.

• Merge the two lists while preserving the order of appearance.

• Ensure to handle edge cases like empty list or list with only odd or even numbers.
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Q2. 
Convert Sorted Array to BST Problem Statement
Given a sorted array of length N, your task is to construct a balanced binary search tree (BST) from the array. If multiple balanced BSTs are possible, you ca...read more
Ans. 
Construct a balanced binary search tree from a sorted array.
• Create a function that recursively constructs a balanced BST from a sorted array.

• Use the middle element of the array as the root of the BST.

• Recursively build the left and right subtrees using the elements to the left and right of the middle element.

• Ensure that the left and right subtrees are also balanced BSTs.

• Return 1 if the constructed tree is correct, other
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Q3. What is the difference between the MVC (Model-View-Controller) and MVT (Model-View-Template) design patterns?
Ans. 
MVC focuses on separating concerns of an application into three components, while MVT is a variation used in Django framework.
• MVC separates an application into Model (data), View (presentation), and Controller (logic) components.

• MVT is used in Django framework where Model represents data, View represents presentation, and Template represents logic.

• In MVC, the Controller handles user input and updates the Model and View...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round with questions based on DSA, OOPS and puzzles.

Q1. 
Reverse Linked List Problem Statement
Given a Singly Linked List of integers, your task is to reverse the Linked List by altering the links between the nodes.
Input:
The first line of input is an intege...read more
Ans. 
Reverse a singly linked list by altering the links between nodes.
• Iterate through the linked list and reverse the links between nodes

• Use three pointers to keep track of the current, previous, and next nodes

• Update the links between nodes until the end of the list is reached
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Q2. 
Reverse Number Problem Statement
Ninja is exploring new challenges and desires to reverse a given number. Your task is to assist Ninja in reversing the number provided.
Note:
If a number has trailing ze...read more
Ans. 
Implement a function to reverse a given number, omitting trailing zeros.
• Create a function that takes an integer as input and reverses it while omitting trailing zeros

• Use modulo and division operations to extract digits and reverse the number

• Handle cases where the reversed number has leading zeros by omitting them

• Ensure the reversed number is within the constraints specified
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Q3. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from end to start and append each character to a new string.

• Use built-in functions like reverse() or slicing to reverse the string.

• Handle special characters and numbers while reversing the string.

• Ensure to consider the constraints provided in the problem statement.
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Q4. What is overloading in the context of Object-Oriented Programming (OOP)?
Ans. 
Overloading in OOP is the ability to define multiple methods with the same name but different parameters.
• Overloading allows multiple methods with the same name but different parameters to coexist in a class.

• The compiler determines which method to call based on the number and type of arguments passed.

• Example: having multiple constructors in a class with different parameter lists.
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with question based on Web Dev, Cloud Computing, Networking etc.

Q1. What is TELNET?
Ans. 
TELNET is a network protocol used to establish a connection with a remote computer over a network.
• TELNET stands for Telecommunication Network.

• It allows a user to log in to a remote computer and execute commands as if they were directly connected to that computer.

• TELNET operates on port 23.

• It is not secure as the data is transmitted in plain text.

• SSH (Secure Shell) is a more secure alternative to TELNET.
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Q2. What is the difference between TELNET and SSH?
Ans. 
TELNET is insecure, while SSH is secure for remote access to servers.
• TELNET sends data in plain text, while SSH encrypts data for secure communication

• SSH uses public-key cryptography for authentication, TELNET does not

• SSH provides secure remote access to servers, TELNET does not prioritize security

• TELNET operates on port 23, while SSH operates on port 22
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Q3. 
Problem: Sort an Array of 0s, 1s, and 2s
Given an array/list ARR consisting of integers where each element is either 0, 1, or 2, your task is to sort this array in increasing order.
Input:
The input sta...read more
Ans. 
Sort an array of 0s, 1s, and 2s in increasing order.
• Use a three-pointer approach to partition the array into sections of 0s, 1s, and 2s.

• Iterate through the array and swap elements based on their values.

• Time complexity should be O(n) to meet the constraints.
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Q4. What is a hypervisor?
Ans. 
A hypervisor is a software that creates and runs virtual machines on a physical host machine.
• Hypervisors allow multiple operating systems to run on a single physical machine

• They provide isolation between virtual machines

• Examples include VMware ESXi, Microsoft Hyper-V, and KVM
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Q5. Can you explain cloud computing in layman’s terms?
Ans. 
Cloud computing is like renting a computer over the internet instead of owning one.
• Cloud computing allows users to access and store data and applications over the internet instead of on their own physical computer.

• It offers scalability, flexibility, and cost-effectiveness as users can easily adjust their storage and computing needs.

• Examples include services like Amazon Web Services (AWS), Microsoft Azure, and Google Cl
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Q6. What are the stages in the Software Development Life Cycle?
Ans. 
The stages in the Software Development Life Cycle include planning, design, development, testing, deployment, and maintenance.
• 1. Planning: Define project scope, requirements, and timelines.

• 2. Design: Create architecture, UI/UX, and database design.

• 3. Development: Write code based on design specifications.

• 4. Testing: Verify functionality, performance, and security.

• 5. Deployment: Release the software to users or clients.

• ...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions based on DSA and OOPS. A detailed discussion on my projects was also carried out.

Q1. 
Common Elements in Three Sorted Arrays
Given three sorted arrays A, B, and C of lengths N, M, and K respectively, your task is to find all elements that are present in all three arrays.
Input:
The first...read more
Ans. 
Find common elements in three sorted arrays and output them in order.
• Iterate through all three arrays simultaneously using three pointers.

• Compare elements at pointers and move pointers accordingly.

• If elements are equal, add to result and move all pointers forward.

• If elements are not equal, move pointer of smallest element forward.
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Q2. What is a volatile variable?
Ans. 
A volatile variable is a variable that can be modified by multiple threads simultaneously.
• Volatile variables are used in multithreading to ensure visibility of changes made by one thread to other threads.

• They are not cached in thread's local memory, but always read from main memory.

• They are typically used for flags or status variables that are accessed by multiple threads.

• Example: 'volatile boolean flag = true;'
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Q3. Can you explain the concept of multithreading in Java?
Ans. 
Multithreading in Java allows multiple threads to execute concurrently, improving performance and responsiveness.
• Multithreading allows multiple threads to run concurrently within a single process.

• Threads share the same memory space, allowing for efficient communication and data sharing.

• Java provides built-in support for multithreading through the Thread class and Runnable interface.

• Example: Creating a new thread using ...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.

Q1. Data structures, Algorithm
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The task was a Codility type

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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