Practo Senior Android Developer Interview Questions and Answers

Q1. Explain Deadlock?
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Q2. Explain Red Black Tree?
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Q3. Find local minima in a 1-D array?
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Q4. Find local minima in 2-D array?
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Majorily on SQL and Databases

Q1. Align two images in a page with same width and same height
Ans. 
Use CSS to align two images with same width and height on a page
• Set both images to have the same width and height using CSS

• Use flexbox or grid layout to align the images horizontally or vertically

• Adjust margins or padding to fine-tune the alignment
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Q2. Array related question
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Q1. Situation based question
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Q2. Majorily focused on project
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Q1. React JS, coding round, DSA, poly phill, map , shallow copy deep copy, popular JS DSA questions
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Basic React JS clock/ stopwatch

2 coding question one on maximum sum problem and other on tree traversal

Q1. Dbms oops dsa questions are there and one coding question which you have to pseudo code it and dry run it
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Round duration - 60 Minutes
Round difficulty - Medium

It has 3 Coding Questions of medium-hard level and the time limit was 1 hour only. I don’t exactly remember the questions but I was able to do only two of them completely.

Q1. 
Biggest Number Formation Problem
Your task is to construct the largest number possible by concatenating each of the provided positive integers in the array exactly once.
Input:
Integer T denoting the nu...read more
Ans. 
Construct the largest number by concatenating positive integers in the array exactly once.
• Sort the array of integers in a way that the concatenation of the numbers forms the largest possible number.

• Use a custom comparator function to sort the numbers based on their concatenated values.

• Join the sorted array elements to form the final largest number.
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Q2. 
Number of Longest Increasing Subsequence Problem Statement
Given an integer array ARR of length N, determine the count of longest increasing subsequences present in the array.
Explanation:
The Longest I...read more
Ans. 
Count the number of longest increasing subsequences in an integer array.
• Identify the longest increasing subsequences in the array

• Count the number of such subsequences

• Consider the constraints while implementing the solution

• Examples: For input [50, 3, 90, 60, 80], the output is 2
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Round duration - 60 Minutes
Round difficulty - Medium

First, the interviewer introduced himself and then asked to introduce myself. Then he asked about the projects I did. After an introductory discussion on projects, he gave me 3 coding questions on their personal live code environment.

He asked me to explain the approach first and then code it down. I had to explain the time complexity of each solution and optimal code if possible with lesser time complexity.

Q1. 
Cache Operations Problem
You are provided with a cache that can hold a maximum of 'N' elements. Initially, this cache is empty. There are two main operations you can perform on this cache:
Explanation:
...read more
Ans. 
Implement a cache with insert, update, and retrieve operations, returning results of retrieve operations in order.
• Create a cache data structure with specified size 'N'.

• Implement insert and update operations based on the given criteria.

• For retrieve operation, return the value associated with the 'U_ID' if present, else return -1.

• Handle cases where the cache is full and least frequently used items need to be removed.

• Retu...read more
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Q2. 
Possible Words from a Phone Number: Problem Statement
Given a string S composed of digits ranging from 2 to 9, determine all possible strings that can be created by mapping these digits to their correspon...read more
Ans. 
Given a phone number, generate all possible words by mapping digits to letters on a T9 keypad.
• Create a mapping of digits to letters on a T9 keypad

• Use recursion to generate all possible combinations of letters for the given phone number

• Sort the resulting strings in lexicographical order
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Q3. 
Shortest Unique Prefix Problem
You are given an array containing N words. Your task is to derive the shortest prefix for each word that uniquely identifies it amongst the other words. For instance, given t...read more
Ans. 
Given an array of words, find the shortest unique prefix for each word.
• Create a Trie data structure to efficiently store and search for prefixes.

• Traverse the Trie to find the shortest unique prefix for each word.

• Return the list of shortest unique prefixes for all words.
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Round duration - 60 Minutes
Round difficulty - Hard

In this round interviewer gave me 2 coding questions and asked me to code on any editor of my choice. I opened VS code to code those problems.

Q1. 
Maximum Subarray Sum Problem Statement
Given an array arr of length N consisting of integers, find the sum of the subarray (including empty subarray) with the maximum sum among all subarrays.
Explanation...read more
Ans. 
Find the sum of the subarray with the maximum sum among all subarrays in a given array.
• Iterate through the array and keep track of the maximum sum subarray seen so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Handle cases where all elements are negative by returning the maximum element in the array.

• Consider the sum of an empty subarray as 0.
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Q2. 
LRU Cache Implementation
Design and implement a data structure for the Least Recently Used (LRU) cache, which supports the following operations:
1. get(key) - Return the value associated with the key if ...read more
Ans. 
Implement a Least Recently Used (LRU) cache data structure with get and put operations.
• Use a combination of a hashmap and a doubly linked list to efficiently implement the LRU cache.

• Keep track of the least recently used item and remove it when the cache reaches its capacity.

• Update the position of an item in the cache whenever it is accessed or updated.

• Ensure constant time complexity for both get and put operations by u...read more
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Round duration - 40 Minutes
Round difficulty - Easy

The interviewer was very friendly. He asked me about myself and previous interviews.

Round duration - 90 minutes
Round difficulty - Medium

There were a total of 3 coding questions to be solved, and the time limit was 90 minutes. The candidate was free to use language of their choice.

Q1. 
Longest Palindromic Subsequence Problem Statement
Given a string A consisting of lowercase English letters, determine the length of the longest palindromic subsequence within A.
Explanation:
• A subsequ...read more
Ans. 
The task is to find the length of the longest palindromic subsequence in a given string.
• A subsequence is a sequence generated from a string after deleting some or no characters of the string without changing the order of the remaining string characters.

• A string is said to be palindrome if the reverse of the string is the same as the actual string.

• Find the longest palindromic subsequence by considering all possible subs...read more
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Round duration - 45 minutes
Round difficulty - Easy

The first round of interview lasted for around 45 minutes. I was asked two DSA questions, and was supposed to code them while my screen was shared. I wrote code for both the questions with little help from the interviewer. Finally, I was asked couple of questions based on my resume.

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.
...read more
Ans. 
The task is to merge two sorted linked lists into a single sorted linked list.
• Create a new linked list to store the merged list

• Compare the values of the nodes from both lists and add the smaller value to the new list

• Move the pointer of the list with the smaller value to the next node

• Repeat the comparison and addition until one of the lists is empty

• Add the remaining nodes from the non-empty list to the new list

• Return th
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Q2. 
Rotational Equivalence of Strings Problem Statement
Given two strings 'P' and 'Q' of equal length, determine if string 'P' can be transformed into string 'Q' by cyclically rotating it to the right any num...read more
Ans. 
The task is to check if one string can be converted into another string by cyclically rotating it to the right any number of times.
• Iterate through each character of the first string and check if it matches the corresponding character in the second string after a certain number of cyclic rotations.

• If all characters match for any number of cyclic rotations, then the first string can be converted into the second string.

• Us...read more
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Round duration - 30 minutes
Round difficulty - Medium

I was given one data structure question and was then asked about recursion.

Q1. 
Next Greater Element Problem Statement
You are provided with an array or list ARR containing N positive integers. Your task is to determine the Next Greater Element (NGE) for each element in the array.
T...read more
Ans. 
The task is to find the next greater element for each element in an array.
• Iterate through the array from right to left

• Use a stack to keep track of the elements

• For each element, pop elements from the stack until a greater element is found or the stack is empty

• If a greater element is found, it is the next greater element for the current element

• If the stack becomes empty, there is no greater element to the right

• Store the ...read more
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Round duration - 40 minutes
Round difficulty - Easy

This was the hiring manager round. No data structures question were asked in this round. There was discussion around the projects that I had done and my resume. As I am from EEE branch, I was asked why I want to get into software. The interview happened around 8 PM. I was asked to create a schema for one of my projects.

Q1. Why do you want to pursue a career in software?
Ans. 
I want to get into software because of my passion for problem-solving and the opportunity to create innovative solutions.
• Passion for problem-solving

• Opportunity to create innovative solutions

• Interest in technology and its impact on society

• Career growth and job stability

• Flexibility and remote work options
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