ADTRAN Software Developer Interview Questions and Answers

Round duration - 70 Minutes
Round difficulty - Medium

This round had 40 MCQ's followed by 2 questions of DS and Algo. The programming questions were preety standard and can be solved within 30 minutes.

Q1. 
Maximum Subarray Sum Problem Statement
Given an array arr of length N consisting of integers, find the sum of the subarray (including empty subarray) with the maximum sum among all subarrays.
Explanation...read more
Ans. 
Find the sum of the subarray with the maximum sum among all subarrays in a given array.
• Iterate through the array and keep track of the maximum sum subarray seen so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Handle cases where all elements are negative or array is empty.

• Example: For input arr = [-2, 1, -3, 4, -1], the maximum subarray sum is 4.
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Q2. 
Remove Character from String Problem Statement
Given a string str and a character 'X', develop a function to eliminate all instances of 'X' from str and return the resulting string.
Input:
The first lin...read more
Ans. 
Develop a function to remove all instances of a given character from a string.
• Iterate through the string character by character and only add characters that are not equal to the given character to a new string.

• Alternatively, use built-in string manipulation functions to remove all instances of the given character from the string.

• Ensure the function handles edge cases such as empty strings or strings with no instances o...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round had questions from DSA, OS, DBMS and Computer Networks. The programming question was quiet easy and I coded it preety fast after discussing the appropriate approach and complexity analysis.

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 their lengths and the difference in lengths

• Move the pointer of the longer list by the difference in lengths

• Traverse both lists simultaneously until they meet at the merging point
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Q2. Can you explain the concepts of multitasking and multiprogramming?
Ans. 
Multitasking involves executing multiple tasks simultaneously, while multiprogramming involves running multiple programs on a single processor.
• Multitasking allows multiple tasks to run concurrently on a single processor, switching between them quickly.

• Multiprogramming involves loading multiple programs into memory and executing them concurrently, utilizing idle CPU time efficiently.

• Examples of multitasking include runn...read more
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Q3. What is the difference between a process and a program?
Ans. 
A process is an executing instance of a program, while a program is a set of instructions stored in the computer's memory.
• A program is a static set of instructions stored on disk, while a process is a dynamic instance of those instructions being executed in memory.

• Multiple processes can be running the same program simultaneously, each with its own memory space and resources.

• Processes have their own unique process ID (P...read more
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Q4. What is the difference between a process and a thread?
Ans. 
A process is an instance of a program, while a thread is a unit of execution within a process.
• A process has its own memory space, while threads share the same memory space.

• Processes are independent and isolated, while threads can communicate and share resources.

• Creating a new process is more resource-intensive than creating a new thread.

• Processes have their own program counter, while threads share the same program coun...read more
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Q5. What is the main difference between UNION and UNION ALL?
Ans. 
UNION combines and removes duplicate rows, UNION ALL combines without removing duplicates.
• UNION combines the result sets of two or more SELECT statements into a single result set

• UNION removes duplicate rows from the result set

• UNION ALL combines the result sets without removing duplicates

• UNION is slower than UNION ALL as it requires additional processing to remove duplicates

• Use UNION when you want to combine and remove ...read more
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Q6. What are the advantages of using views in a database management system?
Ans. 
Views provide a virtual representation of data, offering advantages such as simplifying complex queries, enhancing security, and improving performance.
• Views simplify complex queries by predefining commonly used joins, filters, and aggregations.

• Views enhance security by allowing users to access only specific columns or rows of a table.

• Views improve performance by storing the results of complex queries, reducing the need...read more
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Q7. What is the ARP protocol?
Ans. 
ARP stands for Address Resolution Protocol, used to map IP addresses to MAC addresses in a local network.
• ARP is used to find the MAC address of a device based on its IP address

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

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

• Example: When a device wants to communicate with another device on the same network, it uses ARP to find the MAC address of the des
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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. Why should we hire you?
Ans. 
I should be hired because of my strong technical skills, problem-solving abilities, and passion for software development.
• I have a solid understanding of data structures and algorithms.

• I have experience in developing and debugging complex software systems.

• I am a quick learner and can adapt to new technologies and programming languages.

• I have a track record of delivering high-quality code on time.

• I am a team player and c...read more
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Q2. What is something about you that is not included in your resume?
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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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