Onsitego Software Developer Interview Questions and Answers

Round duration - 120 minutes
Round difficulty - Medium

This was a 2 hour round consisting of 5 mcqs and 2 codes. The mcqs were pretty much simple based on DS, DBMS, OS, OOP, and C.

Q1. 
Rabbit Jumping Problem
Consider 'n' carrots numbered from 1 to 'n' and 'k' rabbits. Each rabbit jumps to carrots only at multiples of its respective jumping factor A_j (i.e., A_j, 2A_j, 3A_j, ...), for all ra...read more
Ans. 
Calculate uneaten carrots by rabbits with specific jumping factors.
• Iterate through each carrot and check if any rabbit jumps on it.

• Use the jumping factors to determine which carrots are eaten.

• Subtract the eaten carrots from the total to get the uneaten count.
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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 after flipping is greater.

• Return the maximum count of 1s obtained by flipping a sub-array
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Round duration - 60 minutes
Round difficulty - Medium

Started with a brief discussion on my projects and internships. A thorough discussion on whichever languages, frameworks I had used in my projects. Followed by discussion on coding questions. Apart from the codes there were some questions on OS, process stack, heap memory in Java, Garbage collection, OOP principles and comparison based sorting

Q1. 
Sum of Maximum and Minimum Elements Problem Statement
Given an array ARR of size N, your objective is to determine the sum of the largest and smallest elements within the array.
Follow Up:
Can you achie...read more
Ans. 
Find sum of maximum and minimum elements in an array with least number of comparisons.
• Iterate through the array and compare each element with current maximum and minimum to update them.

• Initialize max as smallest possible value and min as largest possible value.

• Return the sum of max and min after iterating through the array.
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Q2. 
Invert a Binary Tree Problem Statement
Given a Binary Tree and one of its leaf nodes, invert the binary tree by following these guidelines:
• The given leaf node becomes the root after the inversion. • F...read more
Ans. 
Invert a binary tree based on a given leaf node as the root.
• Start by finding the leaf node in the binary tree.

• Move the left child of the leaf node to the right side of the leaf node.

• Make the parent of the leaf node the left child of the leaf node.

• Repeat the process for each test case.

• Return the inverted binary tree in level order format.
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Round duration - 60 minutes
Round difficulty - Medium

Questions based on programming, DBMS and puzzles were asked in this round.

Q1. 
Rearrange Array to Form Largest Number
Given an array ARR consisting of non-negative integers, rearrange the numbers to form the largest possible number. The digits within each number cannot be changed.
...read more
Ans. 
Rearrange the array elements to form the largest possible number by concatenating them.
• Sort the array elements in a custom way where the concatenation of two numbers results in a larger number.

• Use a custom comparator function while sorting the array elements.

• Convert the sorted array elements to a single string to get the largest possible number.
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Q2. What is indexing in the context of databases?
Ans. 
Indexing in databases is a technique used to improve the speed of data retrieval by creating a data structure that allows for quick lookups.
• Indexes are created on columns in a database table to speed up the retrieval of rows that match a certain condition.

• They work similar to the index in a book, allowing the database to quickly find the relevant data without having to scan the entire table.

• Examples of indexes include ...read more
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Q3. What are the advantages of B+ Trees in database management systems?
Ans. 
B+ Trees are advantageous in database management systems due to their ability to efficiently store and retrieve data.
• B+ Trees have a high fanout, allowing for more keys to be stored in each node, reducing the height of the tree and improving search performance.

• B+ Trees are balanced trees, ensuring that operations like search, insertion, and deletion have a predictable time complexity of O(log n).

• B+ Trees are optimized ...read more
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Round duration - 45 minutes
Round difficulty - Medium

Puzzles and HR based questions were asked in this round.
He asked questions like : what are my career goals, what do you look forward to in a boss , how do you see yourself in 5 years ,etc etc .

Round duration - 120 minutes
Round difficulty - Medium

The Entire Test is held in HackerRank Platform. It has: 
2 coding questions (one easy and one medium)
2 output questions(medium)
2 Aptitude(easy)
1 general Computer science(medium)
It took me 30 min for each coding questions. I did not know that general question is related to bash commands.
Tips: Practice the Warmup questions in Hacker Rank.
Do some Basic aptitude questions.
Thorough with the basic C and C++ concepts

Q1. 
Binary Tree to Doubly Linked List
Transform a given Binary Tree into a Doubly Linked List.
Ensure that the nodes in the Doubly Linked List follow the Inorder Traversal of the Binary Tree.
Input:
The fi...read more
Ans. 
Convert a Binary Tree into a Doubly Linked List following Inorder Traversal.
• Perform Inorder Traversal of the Binary Tree to get the nodes in order.

• Create a Doubly Linked List by linking the nodes in the order obtained from Inorder Traversal.

• Return the head of the Doubly Linked List as the output.
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Q2. 
Unique Element in Array
Given an arbitrary array arr consisting of N non-negative integers where every element appears thrice except for one. Your task is to find the element in the array that appears onl...read more
Ans. 
Find the unique element in an array where every other element appears thrice.
• Use XOR operation to find the unique element.

• Iterate through the array and XOR each element to find the unique one.

• Return the unique element as the answer.
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Round duration - 60 minutes
Round difficulty - Medium

It's completely around the data structures. The questions are a bit tricky but once u think without any tension u can get through easily. The interviewer is helpful and gives u few hints if u catch them at the right point of time u got it. 
Tips: got through Data Structures and Algorithms Made Easy by Narasimha Karumanchi. It's a best book for the interviews.

Q1. 
Binary Tree Traversals Problem Statement
Given a Binary Tree with 'N' nodes, where each node holds an integer value, your task is to compute the In-Order, Pre-Order, and Post-Order traversals of the binar...read more
Ans. 
Implement a function to compute In-Order, Pre-Order, and Post-Order traversals of a Binary Tree given in level-order format.
• Parse the input level-order tree elements to construct the binary tree.

• Implement recursive functions for In-Order, Pre-Order, and Post-Order traversals.

• Return the traversals as lists of lists for each test case.
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Q2. 
Delete N Nodes After M Nodes in a Linked List
Given a singly linked list and two integers 'N' and 'M', traverse the linked list to retain 'M' nodes and then delete the next 'N' nodes. Continue this proces...read more
Ans. 
Traverse a linked list to retain 'M' nodes and then delete the next 'N' nodes, repeating until the end of the list.
• Create a function that takes the head of the linked list, 'N', and 'M' as input parameters.

• Traverse the linked list, retaining 'M' nodes and deleting the next 'N' nodes in each iteration.

• Update the pointers accordingly to skip 'N' nodes after retaining 'M' nodes.

• Repeat this process until the end of the lin...read more
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Round duration - 60 minutes
Round difficulty - Easy

The interviewer asked to put everything on the blackboard and write down the code of each and everything.

Question : Explain all the search algorithm you know with space and Time complexities. 
Answer : Linear search : It is a sequential search algorithm where the entire array is traversed till the desired element is not found. Time complexity is O(N) and auxiliary space is O(1). 
Binary search : In this algorithm, a sorted array is searched by repeatedly dividing the search interval in half. 
Steps : 
1. Initially the interval covers the whole array.
2. If the value to be searched is less than the item in the middle of the interval, narrow the interval to the lower half. Otherwise, narrow it to the upper half. 
3. The process is repeated until the value is found or the interval is empty.
Time complexity is O(log n) and auxiliary space is O(1) in case of iterative implementation.

Q1. 
Maximum Frequency Number Problem Statement
Given an array of integers with numbers in random order, write a program to find and return the number which appears the most frequently in the array.
If multip...read more
Ans. 
Program to find the number with maximum frequency in an array of integers.
• Create a dictionary to store the frequency of each number in the array.

• Iterate through the array and update the frequency count in the dictionary.

• Find the number with the maximum frequency in the dictionary and return it.

• If multiple elements have the same maximum frequency, return the one with the lowest index.
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Round duration - 60 minutes
Round difficulty - Medium

It was a 60 minute online coding interview where programming questions were discussed.

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Use three pointers to keep track of the current, previous, and next nodes while reversing the linked list.

• Update the head of the reversed linked list as the last node encountered during the reversal process.
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Q2. 
Rearrange Array: Move Negative Numbers to the Beginning
Given an array ARR consisting of N integers, rearrange the elements such that all negative numbers are located before all positive numbers. The orde...read more
Ans. 
Yes, this can be achieved by using a two-pointer approach to rearrange the array in-place with O(1) auxiliary space.
• Use two pointers, one starting from the beginning and one from the end of the array.

• Move the left pointer to the right until it encounters a positive number, and the right pointer to the left until it encounters a negative number.

• Swap the elements at the left and right pointers, and continue this process ...read more
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Round duration - 60 minutes
Round difficulty - Easy

Questions based on data structures , OOPS , Java and operating systems were discussed.

Q1. 
Convert a Binary Tree to its Sum Tree
Given a binary tree of integers, convert it to a sum tree where each node is replaced by the sum of the values of its left and right subtrees. Set leaf nodes to zero.
...read more
Ans. 
Convert a binary tree to a sum tree by replacing each node with the sum of its left and right subtrees, setting leaf nodes to zero.
• Traverse the tree in postorder fashion to calculate the sum of left and right subtrees for each node.

• Set leaf nodes to zero and update the value of each node to the sum of its children.

• Return the level order traversal of the modified tree.
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Q2. Can you explain the concept of the String pool in Java and how garbage collection functionality works?
Ans. 
String pool in Java is a special memory area where String literals are stored to optimize memory usage. Garbage collection in Java is a process of reclaiming memory occupied by objects that are no longer in use.
• String pool is a special area in Java heap memory where String literals are stored to avoid duplicate objects.

• When a new String is created using double quotes, Java first checks the String pool to see if an iden...read more
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Q3. How can you synchronize a HashMap in Java?
Ans. 
You can synchronize a HashMap in Java using the synchronizedMap() method from the Collections class.
• Use synchronizedMap() method to create a synchronized HashMap: Map<String, String> syncMap = Collections.synchronizedMap(new HashMap<>());

• Alternatively, you can use ConcurrentHashMap which is thread-safe and does not require external synchronization.

• Ensure proper synchronization to avoid concurrent modificati
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Round duration - 45 minutes
Round difficulty - Medium

This was CTO round, if you make this round…you are doing pretty good. 
He asked a lot on what I worked on and asked questions relevant to that. Process thread, stacks heaps. A minor system design on component in their system. How they are shared between and trade-off. We discussed about scalability and challenge.

Q1. Can you explain the differences between one-to-one mapping and one-to-many mapping in database design, along with some basic related questions?
Ans. 
One-to-one mapping involves a single relationship between two entities, while one-to-many mapping involves a single entity being related to multiple entities.
• One-to-one mapping: each record in one table is related to only one record in another table.

• One-to-many mapping: each record in one table can be related to multiple records in another table.

• In one-to-one mapping, a foreign key is used to establish the relationship...read more
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Q2. What is the difference between a process and a thread?
Ans. 
A process is an independent entity that contains its own memory space and resources, while a thread is a subset of a process that shares the same memory space and resources.
• A process has its own memory space, while threads within a process share the same memory space.

• Processes are independent entities, while threads are subsets of processes.

• Processes have their own resources like file descriptors and sockets, while thr...read more
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