Zolo Software Developer Interview Questions and Answers

Easy to medium questions, Questions on DSA and Node.js.

Q1. Valid parenthesis
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Q2. Three sum problem
Ans. 
The three sum problem involves finding unique triplets in an array that sum to zero.
• Sort the array to simplify finding triplets.

• Use a loop to fix one element and apply two-pointer technique for the rest.

• Skip duplicates to ensure unique triplets.

• Example: For array [-1, 0, 1, 2, -1, -4], the triplets are [-1, -1, 2], [-1, 0, 1].
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Q1. Build an sample app server with express.js
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Build a sample app server using express.js
• Install express.js using npm

• Create a new express app

• Set up routes and middleware

• Start the server to listen on a specific port
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Q2. How do you make connection with database in your project
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Q3. Write multer middleware code.
Ans. 
Multer is a middleware for handling multipart/form-data, used for file uploads in Node.js.
• Install multer package using npm: npm install multer

• Require multer in your Node.js file: const multer = require('multer')

• Set up multer middleware with desired options: const upload = multer({ dest: 'uploads/' })

• Use the upload middleware in your route handler to process file uploads
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2 Graph question of leetcode

Q1. DSA Questions of leetcode
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Q2. DSA Questions
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Q1. The question was about Nodejs
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Q2. The question was to build a linked list in Nodejs
Ans. 
A linked list in Node.js is a data structure consisting of nodes that hold data and a reference to the next node.
• A linked list consists of nodes, each containing data and a pointer to the next node.

• To create a linked list, define a Node class with properties for data and next.

• Implement methods to add, remove, and traverse nodes in the linked list.

• Example of adding a node: function add(value) { const newNode = new Node(...read more
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Q1. The first question was related to DSA
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Q2. The question was related to SQL
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Sorting of an array and aptitude

Q1. BFS graph traversal
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Q1. Binary tree question
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Round duration - 90 minutes
Round difficulty - Medium

The test was conducted in the evening from 5:00 pm to 6:30 pm. Because of the covid situation, all the students attempted the test from their homes. But it was a webcam-based test to avoid any kind of cheating.
There were 3 coding problems to be done in 90 minutes.
After resume based shortlisting, 70 candidates were selected to appear for the test out of which 30 were shortlisted for interviews.

Q1. 
Amazing Strings Problem Statement
Determine if the third string contains all the characters from both the first and second strings in any order. If so, return "YES"; otherwise, return "NO".
Input:
Line ...read more
Ans. 
Check if the third string contains all characters from the first and second strings in any order.
• Create a frequency map for characters in the first and second strings.

• Check if all characters in the third string are present in the frequency map.

• Ensure the count of characters in the third string matches the count in the frequency map.

• Return 'YES' if all conditions are met, otherwise return 'NO'.
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Q2. 
Shortest Path Visiting All Nodes
You are given a connected undirected unweighted graph comprising 'N' nodes and 'M' edges. In this graph, each pair of connected nodes is linked by exactly one undirected e...read more
Ans. 
Find the length of the shortest path visiting all nodes in a connected undirected unweighted graph.
• Use Breadth First Search (BFS) to find the shortest path that visits all nodes at least once.

• Maintain a bitmask to keep track of visited nodes and their states.

• Consider all possible permutations of nodes to find the shortest path length.
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Q3. 
Meeting Rooms Allocation Problem Statement
Stark Industry is planning to organize meetings for various departments in preparation for Stark Expo. Due to limited rooms in Stark Tower, the goal is to alloca...read more
Ans. 
Determine the minimum number of conference rooms required for scheduling meetings.
• Sort the meetings by start time.

• Iterate through the meetings and keep track of rooms needed based on overlapping times.

• Use a priority queue to efficiently allocate rooms.

• Example: For meetings (1pm-4pm), (3pm-5pm), (4pm-6pm), 2 rooms are required.

• Ensure linear time complexity by optimizing the room allocation process.
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Round duration - 50 minutes
Round difficulty - Medium

This round started at 9 am and went till 4 pm.
Out of 70 students that appeared in online coding test, 30 were shortlisted for the first round (this round) of interviews.
In this round, everyone was asked one moderate level coding question. The interviewer provided the link to an IDE, where I wrote my code.
The interview started with the introduction being followed by 1 coding problem. In the end, the interviewer asked me if I wanted to ask any questions. To which I asked him my feedback so that I can improve my wear areas.
Of the 30 candidates, 17 were selected for the final interview round.

Q1. 
Print All Subsets Challenge
Given an array arr containing 'N' distinct integers, your task is to generate all possible non-empty subsets of this array.
Note: While the elements within each subset should ...read more
Ans. 
Generate all possible non-empty subsets of an array of distinct integers.
• Use recursion to generate all subsets by including or excluding each element in the array.

• Maintain a current subset and add it to the result when reaching the end of the array.

• Ensure elements within each subset are in increasing order.

• Handle the input and output format as specified in the question.
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Round duration - 50 minutes
Round difficulty - Easy

This was a technical + HR round. Started in the evening at 4:30 pm, this round went till 9:30 pm.
17 students were shortlisted for this final round of interview.
This interview was also virtual and involved both technical and HR-related questions. The interview started with an introduction and then questions based on my resume were asked.
Out of 17 candidates, 8 candidates got a full-time offer from Urban Company.

Q1. 
Find Row With Maximum 1's in a Sorted 2D Matrix
You are provided with a 2D matrix containing only the integers 0 or 1. The matrix has dimensions N x M, and each row is sorted in non-decreasing order. Your...read more
Ans. 
Find the row with the maximum number of 1's in a sorted 2D matrix.
• Iterate through each row of the matrix and count the number of 1's in each row.

• Keep track of the row index with the maximum number of 1's seen so far.

• Return the index of the row with the maximum number of 1's.

• If multiple rows have the same number of 1's, return the row with the smallest index.
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