Spinny Frontend Developer Intern Interview Questions and Answers

90 mins, easy, Data structures and algorithm basics

Q1. Given an array, remove all duplicates in place
Ans. 
Remove duplicates from array of strings in place
• Use a HashSet to keep track of unique elements

• Iterate through the array and remove duplicates by checking if element is already in the HashSet

• Update the array in place by shifting elements to fill in the removed duplicates
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Q1. Caching and its uses
Ans. 
Caching is the process of storing data in a temporary location to reduce access time and improve performance.
• Caching helps reduce the load on servers by serving frequently accessed data quickly

• It can improve performance by reducing the time needed to retrieve data from the original source

• Examples include browser caching, CDN caching, and database caching
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Q1. Personality grading
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Q1. Adjacent Robber
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Q2. Vertical Order Traversal
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3-sum leetcode, 4 sum leetcode, react

Round duration - 45 Minutes
Round difficulty - Medium

It was in the mid day and since I applied for a Frontend role the discussion was majorly around data structure and bit of Javascript.
The interviewer was helping and good listener.

Q1. 
Merge Two Sorted Linked Lists Problem Statement
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
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Ans. 
Merge two sorted linked lists into a single sorted linked list without using additional space.
• Create a dummy node to start the merged list

• Compare the values of the two linked lists and add the smaller value to the merged list

• Move the pointer of the merged list and the pointer of the smaller value list

• Continue this process until one of the lists is fully traversed

• Append the remaining elements of the other list to the me
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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 array of 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of 0s, 1s, and 2s while traversing the array.

• Swap elements based on the values encountered to sort the array in-place.

• Time complexity should be O(N) and space complexity should be O(1).
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Round duration - 60 Minutes
Round difficulty - Medium

It was more of a in depth round on the framework I'm working on and problem solving.

Q1. What is the event loop and what is its significance?
Ans. 
The event loop is a mechanism in programming that allows for asynchronous execution of code.
• The event loop is a key component in JavaScript's runtime environment, responsible for handling asynchronous operations.

• It continuously checks the call stack for any pending tasks and executes them in a non-blocking manner.

• The event loop ensures that the program remains responsive by allowing other code to run while waiting for ...read more
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Q2. Can you provide examples of output-based questions in JavaScript that utilize browser APIs?
Ans. 
Output-based questions in JavaScript using browser APIs
• Example 1: Write a script that uses the Geolocation API to display the user's current location on a map

• Example 2: Create a program that uses the Web Audio API to play a sound when a button is clicked

• Example 3: Develop a web page that uses the Canvas API to draw a simple animation
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Q3. How would you design a system to support localization in a mobile app?
Ans. 
Designing a system to support localization in a mobile app
• Use resource files to store localized strings for different languages

• Implement a language selection feature for users to choose their preferred language

• Utilize localization libraries or frameworks to streamline the process

• Consider cultural differences when localizing content, such as date formats and currency symbols
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Round duration - 75 Minutes
Round difficulty - Hard

It was more of a fitment/managerial round.
Didn't had any coding questions, but was asked more on approaches and optimisations.
Discussions on the project you have worked on.

Q1. You need to find the fastest 3 horses out of a group, given that you can only race 5 horses at a time. How would you approach this problem?
Ans. 
To find the fastest 3 horses out of a group with 5 horses racing at a time, we can use a tournament style approach.
• Divide the horses into groups of 5 and race them against each other. This will give you the fastest horse in each group.

• Take the winners from each group and race them against each other. The top 3 horses in this final race will be the fastest 3 overall.

• Keep track of the results and compare the timings to d
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Q2. How do you debug the root cause of lag on a screen?
Ans. 
To debug lag on a screen, analyze code, check for memory leaks, optimize rendering, and use profiling tools.
• Analyze code to identify any inefficient algorithms or operations causing lag.

• Check for memory leaks that could be impacting performance.

• Optimize rendering by reducing the number of draw calls, optimizing shaders, and minimizing overdraw.

• Use profiling tools like Xcode Instruments or Android Profiler to identify p
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Q3. Can you explain the architecture of the app you have recently worked on?
Ans. 
The app I recently worked on is a social media platform for sharing photos and connecting with friends.
• The app follows a client-server architecture, with the client being the mobile app and the server handling data storage and processing.

• The client side is built using React Native for cross-platform compatibility.

• The server side is implemented using Node.js with a MongoDB database for storing user data and photos.

• The a...read more
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Round duration - 120 Minutes
Round difficulty - Medium

Machine Coding Round
2 Hours in Total
15 Mins for Question Explaination and Doubts
1.5 Hours for coding
15 mins to discuss the approach 

Timing - 3 to 5 pm (They are flexible)
Interviewer was very patient and helped me understand the question

Round duration - 60 Minutes
Round difficulty - Medium

2 Data Strucutre Questions
Timing 5-6 pm (They are flexible)
Google Meet
Online IDE

Q1. 
Unique Binary Search Trees Problem Statement
Given an integer 'N', your task is to compute the number of structurally unique BSTs (binary search trees) that can be formed using an exact number of 'N' uniq...read more
Ans. 
The task is to compute the number of structurally unique BSTs that can be formed using an exact number of unique values.
• Use dynamic programming to solve the problem efficiently.

• The number of structurally unique BSTs can be calculated using Catalan numbers.

• For N nodes, the number of structurally unique BSTs is given by the Nth Catalan number.

• Example: For N=3, the number of structurally unique BSTs is 5.
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Q2. 
Subsequences of String Problem Statement
You are provided with a string 'STR' that consists of lowercase English letters ranging from 'a' to 'z'. Your task is to determine all non-empty possible subsequen...read more
Ans. 
Generate all possible subsequences of a given string.
• Use recursion to generate all possible subsequences by including or excluding each character in the string.

• Maintain a current index to keep track of the characters being considered.

• Append the current character to each subsequence generated so far.

• Recursively call the function with the next index to include or exclude the next character.

• Base case: When the current ind...read more
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Round duration - 60 Minutes
Round difficulty - Easy

HIRING MANAGER ROUND

Discussion about the organisation now questions

Dsa question based on dp