Coinbase Software Developer Interview Questions and Answers

Round duration - 150 Minutes
Round difficulty - Medium

3 coding questions and 20 mcq's

Q1. 
Maximum Sum of Two Non-Overlapping Subarrays
Given an integer array ARR and a positive integer K, your task is to determine two non-overlapping subarrays of length K that yield the maximum combined sum.
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Ans. 
The task is to find two non-overlapping subarrays of length K in an array, such that their sum is maximum.
• Iterate through the array and calculate the sum of each subarray of length K

• Store the maximum sum obtained from the first subarray

• Iterate again and calculate the sum of each subarray of length K, excluding the previous subarray

• Store the maximum sum obtained from the second subarray

• Return the sum of the two maximum
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Q2. 
Distinct Subsequences Problem Statement
You are given a string 'S' of length 'N' which may include duplicate alphabets. Your goal is to calculate the number of distinct subsequences in the string.
Exampl...read more
Ans. 
The task is to find the count of distinct subsequences in a given string.
• Use dynamic programming to solve the problem.

• Create a 2D array to store the count of distinct subsequences for each prefix of the string.

• Initialize the first row of the array with 1, as there is only one subsequence of an empty string.

• For each character in the string, calculate the count of distinct subsequences by considering two cases: including...read more
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Q3. 
Array Intersection Problem Statement
Given two integer arrays/ lists ARR1 and ARR2 of sizes N and M respectively, you are required to determine their intersection. An intersection is defined as the set of...read more
Ans. 
The task is to find the intersection of two integer arrays/lists.
• Read the number of test cases

• For each test case, read the size and elements of the first array/list

• Read the size and elements of the second array/list

• Find the intersection of the two arrays/lists

• Print the intersection elements in the order they appear in the first array/list
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Round duration - 120 Minutes
Round difficulty - Medium

Online video call based round, Timing was 10-11 AM
Interview started with basic greetings, post that i explained by projects in brief and then we jumped right into dsa questoins.

Q1. 
Number of Islands Problem Statement
You are given a non-empty grid that consists of only 0s and 1s. Your task is to determine the number of islands in this grid.
An island is defined as a group of 1s (re...read more
Ans. 
The task is to find the number of islands in a grid consisting of 0s and 1s.
• An island is a group of 1s connected horizontally, vertically, or diagonally

• The grid is surrounded by 0s on all four edges

• Use a depth-first search (DFS) or breadth-first search (BFS) algorithm to traverse the grid and count the number of islands

• Initialize a visited array to keep track of visited cells

• For each unvisited cell with a value of 1, p...read more
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Q2. 
Arrangement Problem Statement
Determine the number of permutations of list A = [1, 2, ..., N] such that for every index i, either A[i] is divisible by i or i is divisible by A[i].
Input:
The input start...read more
Ans. 
The goal is to find the number of permutations of a list satisfying certain conditions.
• Iterate through all permutations of the list

• Check if each permutation satisfies the given conditions

• Count the number of permutations that satisfy the conditions

• Return the count for each test case
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Q3. 
Idempotent Matrix Verification
Determine if a given N * N matrix is an idempotent matrix. A matrix is considered idempotent if it satisfies the following condition:
M * M = M
Input:
The first line cont...read more
Ans. 
An idempotent matrix is a square matrix that remains unchanged when multiplied by itself.
• Check if the given matrix satisfies the property M*M = M

• Iterate through each element of the matrix and perform the matrix multiplication

• Compare the result with the original matrix

• If they are equal, return true; otherwise, return false
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Round duration - 120 Minutes
Round difficulty - Easy

This was EM round, started with me explaining my projects in deep and facing some counter questions on that, proceeded to os, dbms basic questions and some low level designing and lastly a puzzle to end interview.

Q1. Can you design an attendance management system?
Ans. 
Design attendance management system
• Create a database to store employee information

• Implement a user interface for employees to mark their attendance

• Develop a system to track and record attendance data

• Generate reports and analytics based on attendance data
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Round duration - 20 Minutes
Round difficulty - Easy

This was formality round, HR came and explained what meesho does and told my joining dates and compensation details.

Q1. Implement an immutable class.
Ans. 
An immutable class is a class whose instances cannot be modified after creation.
• Use final keyword for class declaration to prevent inheritance

• Make all fields private and final to prevent modification

• Do not provide setter methods, only getter methods should be used
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Q2. Implement a springboot service that intercepts http requests.
Ans. 
Implement a Springboot service to intercept HTTP requests.
• Create a Springboot application with necessary dependencies.

• Implement a custom interceptor by extending HandlerInterceptorAdapter.

• Override preHandle and postHandle methods to intercept requests and responses.

• Register the interceptor in the WebMvcConfigurerAdapter configuration class.
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3 Medium level dsa questions

Q1. Lld of cab booking system
Ans. 
The Low Level Design (LLD) of a cab booking system involves detailing the system architecture and components at a lower level of abstraction.
• Identify the main components of the system such as user interface, booking engine, payment gateway, and driver allocation algorithm.

• Define the interactions between these components and how data flows between them.

• Specify the data structures and algorithms used for efficient bookin...read more
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Q2. Discussion about online assesment
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2 medium - question 1 array and 1 dp
1 med to hard - dynamic programming

Q1. System design LLD - Polling System
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Q2. How to implement Concurrency in it.
Ans. 
Concurrency in software development allows multiple tasks to run simultaneously, improving performance and responsiveness.
• Use multithreading to execute multiple tasks concurrently

• Implement asynchronous programming to handle tasks that may take longer to complete

• Use synchronization techniques like locks and semaphores to manage access to shared resources

• Consider using thread pools to manage and reuse threads efficiently
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Dsa question based on dp

3 coding question
2 medium 1 hard

Q1. Online polling system based on OOPs
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Q2. Explaining the above code
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HAckerrank based test