Housing.com 3D Visualiser Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Easy

Myntra had conducted a coding test on campus before the start of the placement season with 2 questions, one on stack and other on DP.
Tips : For the test, the DP question asked was pretty standard, on Longest Common Subsequence. The question on stacks, I don't remember what it was but it was also pretty straight forward. For the test, I would recommend to solve problem from GFG. If they do come to resume shortlisting, they are looking for people who have done good projects and internships.

Q1. 
Longest Common Subsequence Problem Statement
Given two strings STR1 and STR2, determine the length of their longest common subsequence.
A subsequence is a sequence that can be derived from another sequen...read more
Ans. 
The task is to find the length of the longest common subsequence between two given strings.
• Implement a function to find the longest common subsequence between two strings.

• Use dynamic programming to solve this problem efficiently.

• Iterate through the strings and build a matrix to store the lengths of common subsequences.

• Return the length of the longest common subsequence found.
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Round duration - 60 minutes
Round difficulty - Easy

The interview started off with questions on my general interest in Software Development. The first round had two coding questions, I was supposed to write the code on paper. 
For the questions, they asked me to code the solution first. And then gave a specific input and asked me to demonstrate step by step in my code, how it would lead to the correct answer.
Tips: It's ok if you can't code a general solution, if you can write a code which works for the particular input they have given then also it's ok with them. But be thorough with Data structures.

Q1. 
Add Two Numbers as Linked Lists
You are given two singly linked lists, where each list represents a positive number without any leading zeros.
Your task is to add these two numbers and return the sum as ...read more
Ans. 
Add two numbers represented as linked lists and return the sum as a linked list.
• Traverse both linked lists simultaneously while keeping track of carry from previous sum

• Create a new linked list to store the sum, updating the value and carry as needed

• Handle cases where one linked list is longer than the other by adding remaining digits with carry
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Round duration - 60 minutes
Round difficulty - Medium

I wasn't asked to write any code in this interview. They asked me some questions on Machine Learning, because of my projects in them. Then they asked me if I knew graph algorithms. Since I knew BFS and DFS, I told them. They asked the difference between the two. Then they asked me if I knew how to find the shortest distance between two points in a graph. I didn't know Dijkstra's properly but I knew it worked on the greedy approach so was able to tell that. Then they asked me how would I find the second shortest path. I tried to answer it with the same greedy approach, but couldn't arrive at the complete solution.
Tips: They ask a tough theoretical question. It's ok if you don't know the answer, they only look for your approach.

Q1. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal in a disconnected graph starting from vertex 0.
• Use a queue to keep track of nodes to visit next in BFS traversal

• Start traversal from vertex 0 and explore its neighbors first

• Continue exploring neighbors level by level until all nodes are visited

• Ensure to print connected nodes in numerical sort order
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Q2. 
DFS Traversal Problem Statement
Given an undirected and disconnected graph G(V, E), where V is the number of vertices and E is the number of edges, the connections between vertices are provided in the 'GR...read more
Ans. 
DFS traversal to find connected components in an undirected and disconnected graph.
• Perform DFS traversal on each vertex to find connected components

• Maintain a visited array to keep track of visited vertices

• Print the vertices of each connected component in ascending order
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Q3. 
Dijkstra's Shortest Path Problem
Given an undirected graph with ‘V’ vertices (labeled 0, 1, ... , V-1) and ‘E’ edges, where each edge has a weight representing the distance between two connected nodes (X,...read more
Ans. 
Dijkstra's algorithm is used to find the shortest path from a source node to all other nodes in a graph with weighted edges.
• Implement Dijkstra's algorithm to find the shortest path distances from the source node to all other nodes in the graph.

• Use a priority queue to efficiently select the next node with the shortest distance.

• Update the distances of neighboring nodes based on the current node's distance and edge weight...read more
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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 - Easy

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 language.

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 connecting the nodes in the order obtained from Inorder Traversal.

• Return the head of the Doubly Linked List.
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Q2. 
Validate BST Problem Statement
Given a binary tree with N nodes, determine whether the tree is a Binary Search Tree (BST). If it is a BST, return true; otherwise, return false.
A binary search tree (BST)...read more
Ans. 
Validate if a given binary tree is a Binary Search Tree (BST) or not.
• Check if the left subtree of a node contains only nodes with data less than the node's data.

• Check if the right subtree of a node contains only nodes with data greater than the node's data.

• Ensure that both the left and right subtrees are also binary search trees.
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Round duration - 60 minutes
Round difficulty - Easy

3 coding questions were asked in this round.

Q1. 
Sort an Array in Wave Form
You are given an unsorted array ARR. Your task is to sort it so that it forms a wave-like array.
Input:
The first line contains an integer 'T', the number of test cases.
For ea...read more
Ans. 
Sort an array in a wave-like pattern where each element is greater than or equal to its neighbors.
• Iterate through the array and swap elements to form the wave pattern.

• Start by sorting the array in non-decreasing order.

• Then, swap adjacent elements to form the wave pattern.

• Return the modified array as the output.
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Q2. 
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.
• Given a rotated sorted array, perform binary search for each query integer.

• Maintain left and right pointers to search efficiently.

• Return the index of the integer if found, else return -1.
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Q3. 
Running Median Problem
Given a stream of integers, calculate and print the median after each new integer is added to the stream.
Output only the integer part of the median.
Example:
Input:
N = 5  
Stre...read more
Ans. 
Calculate and print the median after each new integer is added to the stream of integers.
• Use a min heap to store the larger half of the numbers and a max heap to store the smaller half.

• Keep the sizes of the two heaps balanced to efficiently calculate the median.

• When a new integer is added, adjust the heaps accordingly and calculate the median.

• Output only the integer part of the median after each new integer is added.
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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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