AppyHigh Fullstack Developer Intern Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Level Order Traversal Problem Statement
Given a binary tree of integers, return the level order traversal of the binary tree.
Input:
The first line contains an integer 'T', representing the number of te...read more
Ans. 
Return the level order traversal of a binary tree given in level order with null nodes represented by -1.
• Create a queue to store nodes for level order traversal

• Start with the root node and add it to the queue

• While the queue is not empty, dequeue a node, print its value, and enqueue its children

• Repeat until all nodes are traversed in level order
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Round duration - 45 minutes
Round difficulty - Easy

Q1. What is a deadlock in DBMS, and can you explain the concepts of join and query?
Ans. 
A deadlock in DBMS occurs when two or more transactions are waiting for each other to release locks, causing them to be stuck indefinitely.
• Deadlock is a situation where two or more transactions are unable to proceed because each is waiting for the other to release locks.

• To prevent deadlocks, DBMS uses techniques like deadlock detection and prevention algorithms.

• Joins in DBMS are used to combine rows from two or more ta...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. Design a system for Twitter, outlining the key components and architecture involved.
Ans. 
Design a system for Twitter
• Key components: user profiles, tweets, hashtags, timelines

• Architecture: microservices, load balancers, databases, caching

• Scalability: sharding, replication, CDN

• Real-time processing: streaming APIs, push notifications
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Maximum Subarray Sum Queries
You are provided with an array of ‘N’ integers and ‘Q’ queries. Each query requires calculating the maximum subarray sum in a specified range of the array.
Input:
The first ...read more
Ans. 
Implement a function to calculate maximum subarray sum queries in a given range of an array.
• Iterate through each query and calculate the maximum subarray sum within the specified range using Kadane's algorithm.

• Keep track of the maximum sum found so far and update it as needed.

• Return the maximum subarray sum for each query in the test case.
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an integer array containing only 0s, 1s, and 2s in linear time complexity.
• Use a single scan over the array to sort it in-place.

• Maintain three pointers for 0s, 1s, and 2s and swap elements accordingly.

• Example: Input: [0, 2, 1, 2, 0], Output: [0, 0, 1, 2, 2]
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Round duration - 20 Minutes
Round difficulty - Medium

10 core subject MCQs along with 3 coding questions

1 Fizz Buzz questions
2 third largest string in array of strings
3 operation on numbers given by strings

Q1. Almost all Basic concepts retlated to OS ie process, threads, multitasking, multiprogramming
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Q2. Concepts related to AWS
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Q3. Coding questions like 1. second largest element in array 2. stack implementation and its real time uses 3. frequency of characters in string
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Q1. Deep concepts related to CNS , related to your own laptop its processor , cores etc
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Q2. Top View of binary treee
Ans. 
Top view of binary tree is the nodes visible when viewed from the topmost node.
• Top view shows the nodes visible from the root node's perspective.

• Nodes are printed in the order of their horizontal distance from the root node.

• If two nodes have the same horizontal distance, the node that appears first in the level order traversal is printed first.
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Round duration - 50 minutes
Round difficulty - Medium

First round was a basic javascript problem-solving round. The interviewer judged my grasp on fundamental javascript concepts like objects, closures, polyfills, etc. It was during the afternoon and was conducted on google meet and leetcode playground.
The interviewer was very calm. I was first asked some general questions like why I'm applying for this role and what are the projects I've done.

Q1. 
Search in a Row-wise and Column-wise Sorted Matrix Problem Statement
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...read more
Ans. 
This question asks to find the position of a target integer in a row-wise and column-wise sorted matrix.
• Iterate through each row and column of the matrix

• Compare the target integer with the current element

• If the target integer is found, return the position as {i, j}

• If the target integer is not found, return {-1, -1}
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Round duration - 40 minutes
Round difficulty - Easy

One DSA Question along with some javascript questions were asked like hoisting, difference between JSX and Javascript etc.

Q1. 
Trapping Rain Water Problem Statement
You are given a long type array/list ARR of size N, representing an elevation map. The value ARR[i] denotes the elevation of the ith bar. Your task is to determine th...read more
Ans. 
The question asks to find the total amount of rainwater that can be trapped in the given elevation map.
• Iterate through the array and find the maximum height on the left and right of each bar.

• Calculate the amount of water that can be trapped at each bar by taking the minimum of the maximum heights on the left and right.

• Sum up the trapped water for all bars and return the total amount.
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Round duration - 45 Minutes
Round difficulty - Easy

It was a DSA round where I was asked 2 coding questions and optimised approaches for both.

Q1. 
Ninja and His Meetings Problem Statement
Ninja has started a new startup with a single conference room available for meetings. Given an array/list MEETINGS of consecutive appointment requests, Ninja must ...read more
Ans. 
Find the maximum total booked minutes possible in a conference room for all meetings with a 15-minute break between meetings.
• Iterate through the list of meeting durations and calculate the maximum total booked minutes considering the 15-minute break constraint.

• Keep track of the total booked minutes and skip consecutive meetings that violate the break constraint.

• Return the maximum total booked minutes for each test case
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Q2. 
Trapping Rain Water II Problem Statement
Given an M * N matrix where each cell's value represents its height in a 2-D elevation map, calculate the total volume of water that can be trapped after rainfall.
...read more
Ans. 
Calculate the total volume of water that can be trapped in a 2-D elevation map after rainfall.
• Iterate through each cell in the matrix and calculate the trapped water based on the surrounding heights.

• Use a stack or queue to keep track of the cells to be processed.

• Consider edge cases such as when the matrix is empty or has only one row or column.
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Round duration - 45 Minutes
Round difficulty - Medium

It was more of discussion around my projects and resume. Also asked some questions related to me. What are your hobbies? Willing to relocate?

Q1. 
Smallest Subarray With K Distinct Elements
Given an array A consisting of N integers, your task is to find the smallest subarray of A that contains exactly K distinct integers.
If multiple such subarrays...read more
Ans. 
Find the smallest subarray with exactly K distinct elements in an array.
• Use a sliding window approach to keep track of the subarray with K distinct elements.

• Maintain a hashmap to count the frequency of each element in the window.

• Update the window size based on the number of distinct elements.

• Return the smallest subarray with K distinct elements.
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Q1. Design LLD for Parking Lot
Ans. 
Design LLD for Parking Lot
• Create classes for ParkingLot, ParkingSpot, Vehicle, etc.

• Implement methods for parking, unparking, checking availability, etc.

• Consider different types of vehicles and parking spots (e.g. regular, handicapped, electric)

• Include features like ticketing system, payment processing, and security measures
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Q1. What is closure? Application and concept understanding
Ans. 
Closure is a function that captures the environment in which it was created, allowing it to access variables from that environment even after the function has finished executing.
• Closure allows a function to access variables from its outer scope even after the function has finished executing.

• It 'closes over' the variables from the outer scope, preserving their values.

• Example: function outerFunction() { let outerVar = 'I...read more
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Q2. What is event loop?
Ans. 
Event loop is a mechanism that allows for asynchronous programming by handling and executing events in a loop.
• Event loop is a part of the runtime environment that listens for events and executes callback functions.

• It allows for non-blocking I/O operations by delegating tasks to the operating system.

• Event loop is commonly used in JavaScript for handling asynchronous operations like setTimeout, setInterval, and AJAX requ
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