Hitachi Digital Services Golang Developer Interview Questions, Process, and Tips

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 - 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.

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 - 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.