Housing.com Software Engineer Interview Questions, Process, and Tips

Round duration - 60 minutes
Round difficulty - Easy

Technical round with questions based on data structures and algorithms.

Q1. 
Count Inversions Problem Statement
Given an integer array ARR of size N, your task is to find the total number of inversions that exist in the array.
An inversion is defined for a pair of integers in the...read more
Ans. 
The idea is to use a method similar to the merge sort algorithm. Like merge sort, divide the given array into two parts. For each left and right half, count the inversions, and at the end, sum up the inversions from both halves to get the resultant inversions.
Algorithm: 
1. Divide the array into two equal or almost equal halves in each step until the base case is reached.
2. Create a function merge that counts the n...read more
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Q2. 
Add Two Numbers Represented as Linked Lists
Given two linked lists representing two non-negative integers, where the digits are stored in reverse order (i.e., starting from the least significant digit to ...read more
Ans. 
For every digit in the number, make a new node and attach it to the previous node in the list. 
Steps:
1. Run a while loop while the number > 0. 
2. Extract digit from the number by num%10 and update number to num%10. 
3. Make a new node with its value as the digit and attach it at the end of the list created. 
4. Return the head of the list created.
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Q3. 
Connect Nodes at the Same Level
Given a binary tree where each node has at most two children, your task is to connect all adjacent nodes at the same level. You should populate each node's 'next' pointer t...read more
Ans. 
Level order traversal can be used to solve this problem. Modify queue entries to store the node and the level of nodes. So, the queue node will contain a pointer to a tree node and an integer level. When we deque a node we can check the level of dequeued node. If it is same, set the right pointer of the node to the front node of the queue. 
Time Complexity : O(N) 
Space Complexity :O(N)
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Round duration - 60 minutes
Round difficulty - Easy

Technical round with questions based on data structures and algorithms.

Q1. 
Word Ladder Problem Statement
Given two strings, BEGIN and END, along with an array of strings DICT, determine the length of the shortest transformation sequence from BEGIN to END. Each transformation inv...read more
Ans. 
BFS can be used to solve this question. 
1. Start from the given start word and push it in queue. 
2. Maintain a variable to store the steps needed. 
3. Run a loop until the queue is empty : 
2.1 Traverse all words that are adjacent (differ by one character) to it and push the word in the queue. 
4. Keep doing so until we find the target word or we have traversed all words. Keep Incrementing the ste...read more
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Q2. 
Ninja and Sorted Array Merging Problem
Ninja is tasked with merging two given sorted integer arrays ARR1 and ARR2 of sizes 'M' and 'N', respectively, such that the merged result is a single sorted array w...read more
Ans. 
A simple approach would be to create a new arrays with size as sum of the sizes of both the arrays. Copy the elements of both the arrays in the new array and sort the array. 

A space optimized approach also exists. While traversing the two sorted arrays parallelly, if we encounter the jth second array element is smaller than ith first array element, then jth element is to be included and replace some kth element in...read more
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Q3. 
Count Ways to Reach the N-th Stair Problem Statement
You are provided with a number of stairs, and initially, you are located at the 0th stair. You need to reach the Nth stair, and you can climb one or tw...read more
Ans. 
The question can be approached using recursion. The person can reach nth stair from either (n-1)th stair or from (n-2)th stair. Hence, for each stair n, find out the number of ways to reach n-1th stair and n-2th stair and add them to give the answer for the nth stair. Therefore the expression for such an approach comes out to be : ways(n) = ways(n-1) + ways(n-2)

This is an expression for Fibonacci numbers only, where wa...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on data structures and algorithms.

Q1. 
Shortest Bridge Problem Statement
Two characters, Tony Stark and Thanos, reside on two separate islands within a 2-D binary matrix of dimensions N x M. Each matrix cell has a value of either 1 (land) or 0...read more
Ans. 
Concept of Longest Increasing Subsequence can be used in this problem.
Steps: 
1. Sort the north-south pairs on the basis of increasing order of south x-coordinates. If two south x-coordinates are same, then sort on the basis of increasing order of north x-coordinates.
2. Now , use LIS to find the Longest Increasing Subsequence of the north x-coordinates. Here, in the increasing subsequence , a value can be greater a
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Q2. 
Overlapping Intervals Problem Statement
You are given the start and end times of 'N' intervals. Write a function to determine if any two intervals overlap.
Note:
If an interval ends at time T and anothe...read more
Ans. 
The brute force approach would be to traverse the array and run a nested loop. For each interval, count the number of intervals it intersects and at last, print the maximum number of intervals that an interval can intersect.
The above approach can be optimized counting the number of intervals that do not intersect. The intervals that do not intersect with a particular interval can be divided into two disjoint categories...read more
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Q3. 
Fixing a Swapped Binary Search Tree
Given a Binary Search Tree (BST) where two nodes have been swapped by mistake, your task is to restore or fix the BST without changing its structure.
Input:
The first...read more
Ans. 
Recursion can be used here. Maintain two pointers, first and second to find the 2 nodes that violate the order. At last, change the values of the two nodes by their value. 

PseudoCode : 

correctBST(Node root) {
help(root);
swap(first->val, second->val);
}

help(Node root){
if(root is NULL) return;
help(root->left);
if(first is NULL and prev->val >= root->val) first=prev;
if(first is not NULL and prev-&...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on System design and data structures and algorithms.

Q1. How would you implement a Ctrl+F (find) functionality in a file?
Ans. 
Tip 1: Hash map can be used as a data structure to implement this functionality. According to the type of data stored in the file, a combination of data structures can be used to implement insert() and search() functionality.
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical round with questions on CSS and Node js.
Tip : Have a basic knowledge about : SASS,Susy,Jade,npm,grunt,gulp,yeoman,LibSASS

Q1. What are the different attributes of the CSS position property?
Ans. 
The CSS position property has 4 possible attributes: Static, Relative, Absolute and Fixed.
Static : The default or 'natural' position of block elements on the page. 
Relative : Relative to the placement of the element within the flow of the document.
Absolute : Removes the element from the flow of content and allows it to be positioned in relation to the HTML document.
Fixed : Removes elements from the flow of the HTM
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Q2. What are the data types that SassScript supports?
Ans. 
SassScript supports seven main data types

Numbers ( eg; 1,5 ,10px)
Strings of texts ( g., “foo”, ‘bar’, etc.)
Colors (blue, #04a3f9)
Booleans (true or false)
Nulls (e.g; null)
List of values, separated by space or commas (g., 1.5em, Arial, Helvetica etc.)
Maps from one value to another (g., ( key 1: value1, key 2: Value 2))
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Q3. What are Grunt modules or plugins?
Ans. 
Grunt modules are distributed through Node’s NPM directory. Normally, they are prefixed with grunt- and official grunt plugins are prefixed with grunt-contrib.
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Q4. What is the difference between Sockets and Ajax?
Ans. 
1. The job of web sockets is that it enables client-side JavaScript to open a persistent connection to a server. When web sockets are used, data can be exchanged in the form of a fast message due to this established connection. On the other hand, Ajax enables client-side JavaScript application to make a request to access different server-side resources.
2. Secondly, Ajax can send calls only through the string data type....read more
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical round with questions on Java script, Web Fundamentals etc.
Tip : Have knowledge about Closures,Prototypes,Function/variable hoisting,prototypal inheritance,modular pattern,JSONP,this etc

Q1. How does a server work?
Ans. 
The web browser requests a specific web page – looking for the correct IP address associated with that domain.
The web browser requests a full URL for the site it wants to display – sending this information over to the server.
The web server finds and assembles all the information needed to display the site – including things like ads, dynamic elements, content and more. The server then sends this complete package of inf...read more
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Q2. What is the difference between a function expression and a function declaration?
Ans. 
1. A function declaration must have a function name. A function Expression is similar to a function declaration without the function name.
2. Function declaration does not require a variable assignment. Function expressions can be stored in a variable assignment.
3.Function declarations are executed before any other code. Function expressions load and execute only when the program interpreter reaches the line of code.
4. ...read more
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Round duration - 30 minutes
Round difficulty - Easy

This was a puzzle round. 2 puzzles were given to solve .

Q1. You have a bag of coins, and you need to determine which coins are of different denominations. What strategy would you use to identify the coins?
Ans. 
There is only one bag with forgeries. Ishita can use a simple approach to locate that bag. She must take one coin from the first bag, two coins from the second bag, three coins from the third bag, and ten coins from the tenth bag. She should now just add the weights of all the coins she has chosen.
If there are no forgeries, the total weight should be 55 grams (1+2+3+... +10). If the total weight is 55.3, she can safely...read more
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Q2. The Josephus problem is a theoretical problem related to a certain counting-out game. In this problem, a group of people stands in a circle and every k-th person is eliminated until only one person remains...read more
Ans. 
Let f(n,k) denote the position of the survivor. After the kth person is killed, we're left with a circle of n-1, and we start the next count with the person whose number in the original problem was (k mod n)+1. The position of the survivor in the remaining circle would be f(n-1,k), if we start counting at 1; shifting this to account for the fact that we're starting at (k mod n)+1 yields the recurrence
f(n, k) = ((f(n-1,
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Round duration - 60 minutes
Round difficulty - Easy

Resume based and 1 coding question. Briefly discussed about projects in resume and questions were completely related to projects mentioned.

Q1. 
Find Duplicate in Array Problem Statement
You are provided with an array of integers 'ARR' consisting of 'N' elements. Each integer is within the range [1, N-1], and the array contains exactly one duplica...read more
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Round duration - 60 minutes
Round difficulty - Medium

This round was completely pen and paper coding round. 3 coding questions were asked.

Q1. 
Sum Root to Leaf Numbers
You are given an arbitrary binary tree consisting of N nodes, each associated with an integer value from 1 to 9. Each root-to-leaf path can be considered a number formed by concat...read more
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Q2. 
Subarray Challenge: Largest Equal 0s and 1s
Determine the length of the largest subarray within a given array of 0s and 1s, such that the subarray contains an equal number of 0s and 1s.
Input:
Input beg...read more
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Q3. 
The Skyline Problem
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette when viewed from a distance. Each building is ...read more
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Round duration - 20 minutes
Round difficulty - Easy

Only one coding question was asked with time limit of 10 minutes

Q1. 
Word Break Problem Statement
You are provided with a continuous non-empty string (referred to as 'sentence') which contains no spaces and a dictionary comprising a list of non-empty strings (known as 'wor...read more
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