Arista Networks Staff Engineer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

Need to write working code on a shared document so that the interviewer can see if you can put your ideas into code. In this round, they are not bothered about time complexity of your algorithm. They just wanted to know if you can code whatever you think. So if you do not find best solution also it is OK but write the code for average case at-least.

Q1. 
Problem: Search In Rotated Sorted Array
Given a sorted array that has been rotated clockwise by an unknown amount, you need to answer Q queries. Each query is represented by an integer Q[i], and you must ...read more
Ans. 
Search for integers in a rotated sorted array efficiently.
• Use binary search to find the pivot point where the array is rotated.

• Based on the pivot point, apply binary search on the appropriate half of the array.

• Return the index of the integer if found, else return -1.

• Time complexity should be O(logN) for each query.
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Q2. 
Pair Sum in Binary Search Tree
Given a Binary Search Tree (BST) and a target value 'K', determine if there exist two unique elements in the BST such that their sum equals the target 'K'.
Explanation:
A ...read more
Ans. 
Check if there exist two unique elements in a BST that sum up to a target value 'K'.
• Traverse the BST in-order to get a sorted array of elements.

• Use two pointers approach to find the pair sum in the sorted array.

• Consider edge cases like duplicate elements or negative values.

• Time complexity can be optimized to O(n) using a HashSet to store visited nodes.
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Round duration - 60 minutes
Round difficulty - Medium

I was interviewed for vcloud team so they asked me questions on Cloud, DSA etc.

Q1. 
Reverse List In K Groups Problem Statement
You are provided with a linked list having 'N' nodes and an integer 'K'. Your task is to reverse the linked list in groups of size K. If the list is numbered fro...read more
Ans. 
Reverse a linked list in groups of size K
• Iterate through the linked list in groups of size K

• Reverse each group of nodes

• Handle cases where the last group may have fewer than K nodes
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Q2. 
Reverse Stack with Recursion
Reverse a given stack of integers using recursion. You must accomplish this without utilizing extra space beyond the internal stack space used by recursion. Additionally, you ...read more
Ans. 
Reverse a given stack of integers using recursion without using extra space or loops.
• Use recursion to pop all elements from the original stack and store them in function call stack

• Once the stack is empty, push the elements back in reverse order using recursion

• Use the top(), pop(), and push() methods to manipulate the stack
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Q3. What is cloud computing?
Ans. 
Cloud computing is the delivery of computing services over the internet, including storage, databases, networking, software, and more.
• Cloud computing allows users to access resources on-demand without the need for physical infrastructure.

• Examples of cloud computing services include Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform.

• Cloud computing offers scalability, flexibility, cost-effectiveness, ...read more
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Q4. What are the benefits of cloud computing?
Ans. 
Cloud computing offers scalability, cost-efficiency, flexibility, and improved collaboration.
• Scalability: Easily scale resources up or down based on demand without the need for physical infrastructure.

• Cost-efficiency: Pay only for the resources you use, reducing upfront costs and maintenance expenses.

• Flexibility: Access data and applications from anywhere with an internet connection, enabling remote work and collaborat...read more
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Q5. What are the challenges of cloud computing?
Ans. 
Challenges of cloud computing include security concerns, data privacy issues, and potential downtime.
• Security concerns: Data breaches and unauthorized access are major risks in cloud computing.

• Data privacy issues: Ensuring compliance with regulations like GDPR can be challenging when data is stored in the cloud.

• Potential downtime: Dependence on internet connectivity and cloud service providers can lead to downtime affe...read more
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Round duration - 60 minutes
Round difficulty - Easy

Technical interview round with questions based on DSA and OOPS.

Q1. How do you dynamically allocate a 2D array in C?
Ans. 
Use double pointer to dynamically allocate memory for array of strings in C.
• Declare a double pointer to hold the 2D array of strings.

• Allocate memory for the rows first using malloc.

• Then allocate memory for each string in the row using malloc.

• Assign values to the strings in the array.

• Example: char **array = malloc(rows * sizeof(char *));

• Example: array[i] = malloc(strlen(str) + 1); strcpy(array[i], str);
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Q2. What are virtual functions in C++?
Ans. 
Virtual functions in C++ are functions that can be overridden in derived classes, allowing for polymorphic behavior.
• Virtual functions are declared using the 'virtual' keyword in the base class.

• They are used to achieve runtime polymorphism in C++.

• Derived classes can override the virtual functions defined in the base class.

• Example: class Base { public: virtual void display() { cout << 'Base class dis...read more
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Q3. What are virtual base classes?
Ans. 
Virtual base classes are classes that are inherited virtually to avoid multiple instances of the same base class in a derived class hierarchy.
• Virtual base classes are used in multiple inheritance to prevent the Diamond Problem.

• They are declared with the 'virtual' keyword in the base class.

• When a class inherits a virtual base class, the most derived class is responsible for initializing the virtual base class.

• Example: c...read more
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Round duration - 60 minutes
Round difficulty - Easy

Technical interview round with questions based on OS/Networking etc.

Q1. What is the system call that creates a separate connection?
Ans. 
The system call that creates a separate connection is fork()
• fork() is a system call in Unix-like operating systems that creates a new process by duplicating the existing process

• The new process created by fork() is called the child process, while the original process is called the parent process

• fork() is commonly used in network programming to create separate connections for handling multiple clients
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Q2. What does the epoll_wait() system call do?
Ans. 
epoll_wait() system call waits for events on an epoll instance
• Used in Linux for I/O event notification

• Blocks until one or more file descriptors become ready

• Returns the number of file descriptors ready for I/O operations
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Q3. What are the different protocols used in the transport layer?
Ans. 
Different protocols used in the transport layer include TCP, UDP, SCTP, and DCCP.
• TCP (Transmission Control Protocol) - reliable, connection-oriented protocol used for most internet communication

• UDP (User Datagram Protocol) - connectionless protocol used for applications where speed is more important than reliability

• SCTP (Stream Control Transmission Protocol) - supports multiple streams of data, used for telecommunicati...read more
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Q4. What is the difference between TCP and UDP?
Ans. 
TCP is a connection-oriented protocol that ensures reliable data delivery, while UDP is a connectionless protocol that focuses on speed.
• TCP is reliable and ensures data delivery by establishing a connection before sending data.

• UDP is faster but less reliable as it does not establish a connection before sending data.

• TCP is used for applications that require high reliability and error correction, such as web browsing and...read more
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Round duration - 60 minutes
Round difficulty - Easy

Technical interview round with questions based on Networking etc.

Q1. What is the purpose of ICMP?
Ans. 
ICMP is a protocol used for error reporting, diagnostics, and network management in IP networks.
• ICMP is used to report errors in packet delivery

• It is used for network diagnostics and troubleshooting

• ICMP messages are encapsulated within IP packets

• Examples include ping (echo request/reply) and traceroute
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Q2. What are the types of connection release supported by TCP?
Ans. 
TCP supports four types of connection release: active close, passive close, simultaneous close, and abortive close.
• Active close: Client initiates the connection release process by sending a FIN packet.

• Passive close: Server initiates the connection release process by sending a FIN packet.

• Simultaneous close: Both client and server send FIN packets to each other simultaneously.

• Abortive close: Connection is terminated abru...read more
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Q3. What protocols are used by the MAC layer?
Ans. 
The MAC layer uses protocols like CSMA/CA, CSMA/CD, and TDMA to manage access to the network.
• CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) is used in wireless networks to avoid collisions.

• CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is used in wired networks to detect and handle collisions.

• TDMA (Time Division Multiple Access) is used in networks where devices are assigned specific
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Q4. What is the ARP protocol?
Ans. 
ARP (Address Resolution Protocol) is a protocol used to map an IP address to a MAC address in a local network.
• ARP is used to resolve IP addresses to MAC addresses in a local network.

• It operates at the data link layer of the OSI model.

• ARP requests are broadcasted to all devices on the network.

• Example: When a device wants to communicate with another device on the same network, it uses ARP to find the MAC address correspo
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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.

The task was a Codility type