Arche Softronix Android Developer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Medium

This round was conducted in Hackerrank portal for a total duration of 95 minutes and was divided into 4 sections.

1st Section : Aptitude Section : 14 questions , 28 minutes
2nd Section : Technical Section : 12 questions , 17 minutes
3rd Section :1 coding Questions : 20 minutes+30 minutes

Q1. 
Water Equalization Problem Statement
You are provided with an array ARR of positive integers. Each integer represents the number of liters of water in a bucket. The goal is to make the liters of water in ...read more
Ans. 
Given an array of water buckets, find the minimum liters of water to remove to make all buckets contain the same amount of water.
• Iterate through the array to find the most common amount of water in the buckets.

• Calculate the total liters of water that need to be removed to equalize all buckets to the most common amount.

• Return the total liters of water to be removed.
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Q2. 
Rat in a Maze Problem Statement
You need to determine all possible paths for a rat starting at position (0, 0) in a square maze to reach its destination at (N-1, N-1). The maze is represented as an N*N ma...read more
Ans. 
Find all possible paths for a rat in a maze from source to destination.
• Use backtracking to explore all possible paths in the maze.

• Keep track of visited cells to avoid revisiting them.

• Explore all possible directions (up, down, left, right) from each cell.

• Add the current direction to the path and recursively explore further.

• If the destination is reached, add the path to the list of valid paths.
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Round duration - 120 Minutes
Round difficulty - Medium

This was an Online F2F Technical Round conducted on CodePair : Hackerrank. So, Basically You have to Run and Submit ( Pass All Test cases) in the Interview Round also (Like normal Coding Test) in Codepair : Hackerrank & along with that You should have to explain your Code and Approach to the Interviewers.
The Interviewers were helpful and didn't hesitate in giving hints.
Timing - 10:00 A.M to 12:00 P.M

Q1. 
Minimum Fountains Activation Problem
In this problem, you have a one-dimensional garden of length 'N'. Each position from 0 to 'N' has a fountain that can provide water to the garden up to a certain range...read more
Ans. 
Find the minimum number of fountains to activate to water the entire garden.
• Iterate through the array to find the coverage of each fountain.

• Keep track of the farthest coverage reached by activating fountains.

• Activate the fountain that covers the farthest point not yet covered.

• Repeat until the entire garden is watered.
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Q2. 
Minimize Cash Flow Problem
You are provided with a list of 'transactions' involving 'n' friends who owe each other money. Each entry in the list contains information about a receiver, sender, and the tran...read more
Ans. 
Minimize cash flow problem among friends by optimizing transactions.
• Create a graph where nodes represent friends and edges represent transactions.

• Calculate net amount each friend owes or is owed by summing up all transactions.

• Use a recursive algorithm to minimize cash flow by settling debts between friends.

• Update the graph and repeat the process until all debts are settled.
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Round duration - 120 Minutes
Round difficulty - Hard

A lot of Variants based on Constraints were asked in this Round. They will ask you to write the final code for every question before Submitting it(run all test cases) so you won’t get any hints after running test cases in the IDE. ( So don’t Submit your code before dry running it on a lot of Test Cases on pen & paper , they allow to use pen & blank paper at the time of Interviews) .The Interviewers tried to trick in case of time complexities even if you gave the best one. So try to be confident.

Q1. 
Buy and Sell Stock Problem Statement
Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell ...read more
Ans. 
The task is to determine the maximum profit that can be achieved by performing up to two buy-and-sell transactions on a given set of stock prices.
• Iterate through the array of stock prices and keep track of the maximum profit that can be achieved by buying and selling at different points.

• Maintain variables to store the maximum profit after the first transaction, the maximum profit after the second transaction, and the m...read more
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Round duration - 30 minutes
Round difficulty - Easy

This was HR Round. The HR was friendly and asked basic questions.
The timing was 2:00 PM to 2:30 PM.

Round duration - 120 Minutes
Round difficulty - Easy

The round was conducted in day around 3PM.

Q1. 
Partition Equal Subset Sum Problem
Given an array ARR consisting of 'N' positive integers, determine if it is possible to partition the array into two subsets such that the sum of the elements in both sub...read more
Ans. 
The problem is to determine if it is possible to partition an array into two subsets with equal sum.
• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the results of subproblems.

• Check if the sum of the array is even before attempting to partition it.

• Iterate through the array and update the 2D array based on the sum of subsets.

• Return true if a subset with half the sum is found, false ot
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Round duration - 30 Minutes
Round difficulty - Easy

The interview was preponed and was conducted at 9AM.
The interviewer was friendly and I had saw him earlier at pre-placement talk.

Q1. 
Convert Sentence to Pascal Case
Given a string STR, your task is to remove spaces from STR and convert it to Pascal case format. The function should return the modified STR.
In Pascal case, words are con...read more
Ans. 
Convert a given string to Pascal case format by removing spaces and capitalizing the first letter of each word.
• Iterate through each character in the string

• If the character is a space, skip it

• If the character is not a space and the previous character is a space or it is the first character, capitalize it
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Q2. Write an SQL query to retrieve the Nth highest salary from a database.
Ans. 
SQL query to retrieve the Nth highest salary from a database
• Use the ORDER BY clause to sort salaries in descending order

• Use the LIMIT clause to retrieve the Nth highest salary

• Consider handling cases where there might be ties for the Nth highest salary
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Round duration - 30 Minutes
Round difficulty - Easy

This round was conducted 15mins after 1st round.

Q1. 
Remove the Kth Node from the End of a Linked List
You are given a singly Linked List with 'N' nodes containing integer data and an integer 'K'. Your task is to delete the Kth node from the end of this Lin...read more
Ans. 
Remove the Kth node from the end of a singly linked list.
• Traverse the list to find the length 'N'.

• Calculate the position of the node to be removed from the beginning as 'N - K + 1'.

• Remove the node at the calculated position.

• Handle edge cases like removing the head or tail of the list.

• Update the pointers accordingly after removal.
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Round duration - 60 minutes
Round difficulty - Easy

There was 2 coding questions
Based on ds and algorithms

Q1. 
Ninja's Pattern with Powers of 2
Ninja, who loves playing with numbers, sets out to arrange numbers within 'N' rows. The unique arrangement follows these rules: the first row contains 1 number, the second...read more
Ans. 
Generate a pattern of numbers in rows following a specific sequence based on powers of 2.
• Start with 1 number in the first row, 2 numbers in the second row, 4 numbers in the third row, and so on based on powers of 2.

• Fill the pattern with numbers in increasing sequence from 1 to 9, recycling back to 1 after reaching 9.

• Output the pattern for a given number 'N' of rows.

• Example: For N = 4, the pattern would be 1, 23, 4567,
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Q2. 
Validate Binary Search Tree (BST)
You are given a binary tree with 'N' integer nodes. Your task is to determine whether this binary tree is a Binary Search Tree (BST).
BST Definition:
A Binary Search Tr...read more
Ans. 
Validate if a given binary tree is a Binary Search Tree (BST) or not.
• Check if the left subtree of a node contains only nodes with data less than the node's data.

• Check if the right subtree of a node contains only nodes with data greater than the node's data.

• Recursively check if both the left and right subtrees are also binary search trees.

• Example: For a node with data 4, left subtree nodes (2, 1, 3) are smaller and righ
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Round duration - 60 minutes
Round difficulty - Easy

There was 2 coding questions based on ds and algorithms

Q1. 
Zig-Zag Array Rearrangement
You are provided with an array of distinct elements, and your task is to rearrange the array elements in a zig-zag manner. Specifically, for every odd index i, the element ARR[...read more
Ans. 
Rearrange array elements in a zig-zag manner where every odd index element is greater than its neighbors.
• Iterate through the array and swap elements to satisfy the zig-zag condition.

• Ensure that for every odd index i, ARR[i] > ARR[i-1] and ARR[i] > ARR[i+1].

• Multiple correct answers may exist for a given array.
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Q2. 
Flatten a Linked List
You are provided with a linked list of 'N' nodes. Each node contains two pointers: NEXT, pointing to the next node in the list, and CHILD, pointing to a linked list. Each child linke...read more
Ans. 
Flatten a linked list of sorted child linked lists into a single sorted linked list.
• Traverse the linked list and maintain a priority queue to keep track of the next smallest element.

• Merge the child linked lists into the priority queue while traversing the main linked list.

• Pop elements from the priority queue to create the final flattened linked list.
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Round duration - 45 Minutes
Round difficulty - Medium

My interview started at 9:30 and it took around 45 minutes to complete my interview.This was held on Amazon Chime and the interview lasted for 1 hour. Firstly the interviewer asked to introduce about myself, later asked regarding the projects I have mentioned in my resume. Then started displaying the coding question. The first question is number of islands in a matrix.

Q1. 
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t...read more
Ans. 
Count the number of islands in a 2D matrix of 1s and 0s.
• Use Depth First Search (DFS) or Breadth First Search (BFS) to traverse the matrix and identify connected groups of 1s.

• Maintain a visited array to keep track of visited cells to avoid redundant traversal.

• Increment the island count each time a new island is encountered.

• Consider edge cases like when the matrix is empty or all cells are water (0s).
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Round duration - 90 Minutes
Round difficulty - Easy

Two coding questions were asked and 90 minutes of time was allotted to solve both the problems

Q1. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. 
Given an array of integers and a target, find all pairs of elements that add up to the target.
• Iterate through the array and for each element, check if the target minus the element exists in a hash set.

• If it exists, add the pair to the result. If not, add the element to the hash set.

• Handle cases where the same element is used twice to form a pair.

• Return (-1, -1) if no pair is found.
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Q2. 
Shortest Path in a Binary Matrix Problem Statement
Given a binary matrix of size N * M where each element is either 0 or 1, find the shortest path from a source cell to a destination cell, consisting only...read more
Ans. 
Find the shortest path in a binary matrix from a source cell to a destination cell consisting only of 1s.
• Use Breadth First Search (BFS) algorithm to find the shortest path in the binary matrix.

• Keep track of visited cells to avoid revisiting them.

• Update the path length as you traverse the matrix.

• Return -1 if no valid path exists from source to destination.
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Round duration - 60 Minutes
Round difficulty - Medium

The duration was approx 1 hour. The interview was taken by a young SDE-2.

Q1. 
Character Frequency Problem Statement
You are given a string 'S' of length 'N'. Your task is to find the frequency of each character from 'a' to 'z' in the string.
Example:
Input:
S : abcdg
Output:
1...read more
Ans. 
The task is to find the frequency of each character from 'a' to 'z' in a given string.
• Create an array of size 26 to store the frequency of each character from 'a' to 'z'.

• Iterate through the string and increment the count of the corresponding character in the array.

• Print the array of frequencies as the output.
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Q2. 
Fire in the Cells Problem Statement
Given a matrix MAT of size N * M, where each cell is either on fire or safe, determine if a person can reach an escape cell without being burnt. The person starts from ...read more
Ans. 
Determine if a person can reach an escape cell without encountering fire in a matrix.
• Check if the person can reach an escape cell without encountering fire by simulating the movement of the person and fire spread.

• If the person can reach an escape cell, return the time taken; otherwise, return -1.

• Consider the constraints and edge cases while implementing the solution.
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Round duration - 60 Minutes
Round difficulty - Hard

The interviewer introduced himself and asked me to introduce myself.
I told him about the different projects that I had done and the work in the previous company.
I had worked on AWS(Amazon Web Services) so he asked me all the AWS services that I had worked with and to explain one of them. 
I explained about the working of ECS(Elastic Container Service).
After this, he moved to the coding questions.

Q1. 
Maximum 0-1 Distance Problem Statement
Given a binary matrix of size N*M, find the maximum distance 'di' for every 0-cell to its nearest 1-cell, where the distance is measured using Manhattan distance. Th...read more
Ans. 
Find the maximum Manhattan distance from a 0-cell to its nearest 1-cell in a binary matrix.
• Iterate through the matrix to find all 0-cells and calculate their distances to nearest 1-cells using Manhattan distance formula

• Keep track of the maximum distance found so far and update it if a larger distance is encountered

• Return the maximum distance as the final result
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Q2. 
Search for Indices with Given Difference and Distance
You are provided with an array containing 'N' non-negative integers, along with two other non-negative integers 'K' and 'M'. Your task is to identify ...read more
Ans. 
Find a pair of indices in an array with given difference and distance constraints.
• Iterate through the array and check all possible pairs of indices to satisfy the conditions

• Use nested loops to compare each pair of indices and their corresponding elements

• Return 'valid' if a pair of indices is found that meets the conditions, otherwise return 'invalid'
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Round duration - 60 Minutes
Round difficulty - Medium

The interviewer was a very senior person with at least 10-15 years of experience. He introduced himself and asked me to tell him about myself. (Leadership principle questions followed)
 

Q1. 
Special Binary Tree Problem Statement
Determine whether an arbitrary binary tree is special. A binary tree is called special if every node in this tree has either zero or two children.
Example:
Input:
...read more
Ans. 
Determine if a binary tree is special if every node has zero or two children.
• Traverse the tree and check if each node has either 0 or 2 children.

• Use a recursive approach to check children of each node.

• If any node has only one child, return false immediately.

• Example: For the given input, the output should be true.
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Round duration - 60 Minutes
Round difficulty - Medium

The interview started with introductions and some Leadership principle questions. The interviewer was again a senior person with at least 10-15 years of experience.

I was asked to explain some AWS services.
He asked me to tell about a time when I had a tight deadline and how I worked during it.
He asked me about a time when I took initiative and came up with something new which helped the entire team.
I had prepared well for the LP questions and was able to answer everything.
After this, we move on to coding questions.

Q1. 
Word Presence in Sentence
Determine if a given word 'W' is present in the sentence 'S' as a complete word. The word should not merely be a substring of another word.
Input:
The first line contains an in...read more
Ans. 
Check if a given word is present in a sentence as a complete word.
• Split the sentence into words using spaces as delimiter.

• Check if the given word matches any of the words in the sentence.

• Ensure that the word is not just a substring of another word in the sentence.
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Q2. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Use a combination of hashmap and doubly linked list to implement the LRU cache.

• Keep track of the least recently used item and update it accordingly.

• Ensure to handle cache capacity by evicting the least recently used item when the cache is full.
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