DeHaat Senior Android Developer Interview Questions and Answers

Data Structures, Coding MCQs

Q1. What is Data Structure
Ans. 
Data structures are organized formats for storing, managing, and accessing data efficiently.
• 1. Types: Common data structures include arrays, linked lists, stacks, queues, trees, and graphs.

• 2. Arrays: Fixed-size collections of elements, e.g., [1, 2, 3, 4].

• 3. Linked Lists: Collections of nodes where each node points to the next, e.g., 1 -> 2 -> 3.

• 4. Stacks: Last-in, first-out (LIFO) structures, e.g., function call ...read more
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Q2. Write DFS Algorithm
Ans. 
Depth-First Search (DFS) is a graph traversal algorithm that explores as far as possible along each branch before backtracking.
• DFS uses a stack data structure, either explicitly or via recursion.

• It starts from a selected node and explores each branch before backtracking.

• Example: In a binary tree, DFS can be implemented using pre-order, in-order, or post-order traversal.

• DFS can be used to find connected components in a ...read more
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Round duration - 90 Minutes
Round difficulty - Medium

1 easy and 2 medium-hard DSA problems to solve

Q1. 
Hurdle Game Problem Statement
Kevin is playing a hurdle game where he must jump over hurdles to clear levels. Each level ‘i’ consists of ‘i’ hurdles (e.g., Level 6 has 6 hurdles).
Given the total number ...read more
Ans. 
Given the total number of hurdles Kevin has jumped, determine how many levels he has cleared.
• Iterate through levels while subtracting hurdles from total jumped until remaining hurdles are less than current level

• Return the current level as the number of levels cleared
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Q2. 
N Queens Problem
Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.
Explanation:
A queen can attack another queen if they ar...read more
Ans. 
The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard without threatening each other.
• Use backtracking algorithm to explore all possible configurations.

• Keep track of rows, columns, and diagonals to ensure queens do not threaten each other.

• Generate valid configurations recursively and backtrack when a solution is not possible.
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Q3. 
Count Ways To Travel Triangular Pyramid
Bob is given a triangular pyramid with vertices 'O', 'X', 'Y', and 'Z'. He is also provided with an integer 'N'. Bob can move to any adjacent vertex in a single ste...read more
Ans. 
Calculate the number of ways Bob can complete a journey in a triangular pyramid after N steps.
• Bob can move to any adjacent vertex in a single step

• Bob must return to vertex 'O' after exactly 'N' steps

• Calculate the number of different ways Bob can complete the journey

• Return the result modulo 1000000007

• Consider the constraints provided
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Round duration - 60 Minutes
Round difficulty - Medium

2 DSA problems and computer subject questions

Q1. 
Generate Binary Strings with No Consecutive 1s
Given an integer K, your task is to produce all binary strings of length 'K' that do not contain consecutive '1's.
Input:
The input begins with an integer ...read more
Ans. 
Generate all binary strings of length 'K' with no consecutive '1's in lexicographically increasing order.
• Use backtracking to generate all possible binary strings of length 'K' with no consecutive '1's.

• Start with an empty string and recursively add '0' or '1' based on the condition of no consecutive '1's.

• Sort the generated strings in lexicographically increasing order before outputting them.
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Q2. 
Shuffle Two Strings Problem Statement
You are provided with three strings A, B, and C. The task is to determine if C is formed by interleaving A and B. C is considered an interleaving of A and B if:
• T...read more
Ans. 
Check if a string is formed by interleaving two other strings.
• Iterate through characters of A, B, and C simultaneously to check if C is formed by interleaving A and B.

• Use dynamic programming to efficiently solve the problem.

• Handle edge cases like empty strings or unequal lengths of A, B, and C.

• Example: A = 'aab', B = 'abc', C = 'aaabbc' should return True.
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Round duration - 60 Minutes
Round difficulty - Easy

DSA round

Q1. 
Ninja and Intersection of Lines
You are given coordinates for two lines on a 2D plane: Line 'AB' is defined by points 'A' and 'B', and Line 'PQ' is defined by points 'P' and 'Q'. Your task is to find the ...read more
Ans. 
Find the intersection point of two lines on a 2D plane given their coordinates.
• Calculate the slopes of both lines using the given coordinates.

• Use the slope-intercept form of a line to find the equations of the two lines.

• Solve the equations simultaneously to find the intersection point.

• Return the coordinates of the intersection point with precision up to 6 decimal places.
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Q2. 
Cycle Detection in Directed Graph
Determine if a given directed graph contains a cycle. If the graph has at least one cycle, return true. Otherwise, return false.
Input:
The first line of input contains...read more
Ans. 
Detect cycles in a directed graph and return true if a cycle exists, false otherwise.
• Use Depth First Search (DFS) to detect cycles in the directed graph.

• Maintain a visited array to keep track of visited vertices and a recursion stack to detect back edges.

• If a vertex is visited and is present in the recursion stack, then a cycle exists.

• Example: For the input 4 4, the graph has a cycle 0 -> 1 -> 2 -> 3 -> 1.
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Round duration - 30 Minutes
Round difficulty - Easy

It is a managerial round

Q1. How does a URL work and what is a load balancer?
Ans. 
A URL is a web address that specifies the location of a resource on the internet. A load balancer distributes incoming network traffic across multiple servers to ensure optimal resource utilization and prevent overload.
• A URL (Uniform Resource Locator) is a reference to a web resource that specifies its location on a computer network and the mechanism for retrieving it.

• URLs typically consist of a protocol (such as HTTP ...read more
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3 coding questions on hackerrank medium to hard

Q1. Doctor low level system design question
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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.
...read more
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.

3 Moderate questions were asked. I managed to solve 2 completely and 1 partially.

Q1. Question related to system design were asked.
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Q2. He asked me to design some functions of facebook.
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Q1. Introduction type questions were asked. In this it will prefer only CS students
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There were 2 questions.
1. Knapsack
2. Median in an array

Q1. LLD(machine coding) of Google meet
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Q1. In depth discussion on my projects and resume
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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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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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