80+ Petrocil Engineers Consultants Interview Questions and Answers

An Android photo viewing app with a list of images from disk, one taking half the screen.

• Use RecyclerView to display the list of images

• Use a custom adapter to bind the images to the RecyclerView

• Use a GridLayoutManager with span count of 2 to achieve the half-screen effect

• Load images from disk using a library like Glide or Picasso

• Implement click listeners to handle item selection and display the selected image

Design a screen to show 10 nearest restaurants in a list with uninterrupted scrolling.

• Use a RecyclerView to display the list of restaurants

• Implement a custom adapter to populate the data in the list

• Use a location service to get the user's current location

• Sort the restaurants based on their distance from the user's location

• Load more restaurants as the user scrolls to the end of the list

To search for contacts with duplicate names or numbers, iterate through the list and compare each contact's name and number with the search term.

• Iterate through the list of contacts

• Compare the search term with each contact's name and number

• Return the contacts that match the search term

To search for contacts with duplicate names and numbers, create a search function that checks both fields.

• Create a function that takes a search term as input

• Iterate through the list of contacts

• Check if the search term exists in the Name field or Num field

• Return the contacts that match the search term

To transfer the Ball object from one thread to another, we can use Handler or AsyncTask.

• Use Handler to post a Runnable to the main thread's message queue

• Use AsyncTask to perform background operations and update the UI on the main thread

• Pass the Ball object as a parameter or use a shared variable between threads

To create my own HashMap, I would use an array of linked lists to handle collisions and implement key-value pairs using a hash function.

• Create an array of linked lists to store the key-value pairs

• Implement a hash function to generate an index for each key

• Handle collisions by adding elements to the linked list at the corresponding index

• Support operations like put(key, value), get(key), and remove(key)

Design a screen to show 10 nearest restaurants in a list while keeping the UI uninterrupted.

• Use a scrollable list view to display the restaurants

• Implement a location-based search algorithm to find the nearest restaurants

• Include a search bar to allow users to search for specific restaurants

• Display relevant information for each restaurant such as name, rating, and distance

• Implement filters or sorting options to allow users to customize the list

• Consider using a map view to show ...read more

Looper/handlers allow passing objects between threads in Android.

• Looper is a message loop that runs in a thread and processes messages from a message queue.

• Handlers are used to send messages to the message queue of a looper.

• When an object is passed from one thread to another using a handler, it is encapsulated in a message and added to the receiving thread's message queue.

• The receiving thread's looper then processes the message and delivers it to the handler's callback method...read more

Given an array of natural numbers, find the first missing natural number.

• Sort the array and iterate through it to find the first missing number.

• Use a hash set to keep track of the numbers present in the array.

• The first missing number will be the smallest positive integer not present in the array.

A weather app that displays images for different weather conditions, taking care of half downloaded images and minimizing data consumption.

• Implement image caching to store downloaded images locally

• Check if the image is already downloaded before making a network request

• Use a progress bar to indicate the download status of the image

• Handle cases where the download is interrupted or incomplete

• Implement a mechanism to resume the download from where it left off

• Optimize image loadin...read more

To transfer the Ball object from one thread to another in Android, we can use Handler or AsyncTask.

• Use Handler to post the Ball object from one thread to another

• Create a Handler in the receiving thread and use its post() method to receive the Ball object

• Alternatively, use AsyncTask to perform the transfer in the background thread and update the UI thread with the Ball object

Android components like Recycler View, View Model, ANR are essential for building robust Android applications.

• Recycler View: Efficient way to display large data sets by recycling views as they scroll off the screen.

• View Model: Manages UI-related data in a lifecycle-conscious way, surviving configuration changes.

• ANR (Application Not Responding): Dialog shown to the user when the main thread of an app is blocked for too long.

• Understanding how these components work internally is...read more

Given a point and a radius, find all points in a cartesian plane within the radius.

• Calculate the distance between the given point and all other points in the plane using the distance formula.

• If the distance is less than or equal to the radius, add the point to the result set.

• Return the result set of points within the radius of the given point.

ImageDownloader efficiently handles parallel API calls.

• Use a thread pool to manage parallel API calls.

• Implement caching to avoid redundant API calls.

• Use a priority queue to prioritize image downloads.

• Optimize network requests by using HTTP/2 or multiplexing.

• Consider using a library like Picasso or Glide for image loading and caching.

Deep linking in Android allows users to navigate directly to specific content within an app.

• Deep linking is achieved by defining intent filters in the app's manifest file.

• The intent filter specifies the URL scheme and host that the app can handle.

• When a deep link is clicked, Android checks if any app can handle the URL and prompts the user to choose.

• The chosen app receives the deep link data in the intent's data field.

• Deep linking can be used to open specific screens, perform...read more

To find the 3rd smallest element from an array, sort the array and return the element at index 2.

• Sort the array in ascending order

• Return the element at index 2

• If the array has less than 3 elements, return null

A photo viewer app for Android devices.

• Use RecyclerView to display a grid of photos

• Implement a caching mechanism to improve performance

• Support gestures for zooming and swiping between photos

• Integrate with a cloud storage service for photo storage and retrieval

• Implement a search feature to allow users to find specific photos

STLC stands for Software Testing Life Cycle. It is a process used to test software applications from planning to deployment.

• STLC consists of phases like requirement analysis, test planning, test design, test execution, and test closure.

• As a Senior Software Quality Engineer, I work in different layers of STLC by creating test plans, designing test cases, executing tests, and analyzing results.

• I collaborate with developers, product managers, and other stakeholders to ensure hig...read more

HR is the management of human resources to achieve business goals.

• HR involves recruiting, training, and managing employees.

• HR policies and procedures ensure compliance with laws and regulations.

• HR also includes compensation and benefits management.

• Effective HR planning can help organizations achieve their objectives.

• HR analytics can provide insights into workforce trends and performance.

Design a thread-safe LRU cache that can be scaled.

• Use a ConcurrentHashMap to ensure thread safety.

• Implement a doubly linked list to keep track of the least recently used items.

• Use a HashMap to store the cache items for fast retrieval.

• Implement a size limit for the cache and remove the least recently used item when the limit is reached.

• To scale the cache, use a distributed cache like Redis or Memcached.

Code to get max and second max element of a stack in O(1) complexity.

• Create two variables to store max and second max values

• Update the variables whenever a new element is pushed or popped from the stack

• Return the max and second max values when required

Code to search a given number in a biotonic array with O(logn) time complexity.

• Use binary search to find the peak element in the array.

• Divide the array into two subarrays and perform binary search on each subarray.

• Return the index of the element if found, else return -1.

Launch mode determines how a new instance of an activity is created and added to the task stack.

• Standard: Creates a new instance of the activity each time it is launched.

• SingleTop: If an instance of the activity already exists at the top of the stack, it will be reused.

• SingleTask: If an instance of the activity already exists in the stack, it will be brought to the front and cleared of any activities above it.

• SingleInstance: The activity will be launched in a new task and no ...read more

Stack is a data structure that follows LIFO (Last In First Out) principle.

• Stack holds a collection of elements

• It has two main operations: push (adds element to top) and pop (removes element from top)

• It also has peek operation (returns top element without removing it)

• Stack can be implemented using arrays or linked lists

• Examples: undo-redo functionality in text editors, back-forward navigation in web browsers

Launch mode determines how an activity is launched and how it behaves in the task stack.

• Standard: Creates a new instance of the activity on each launch.

• SingleTop: Reuses the existing instance if it's already at the top of the stack.

• SingleTask: Creates a new task and places the activity at the root of the task.

• SingleInstance: Creates a new task and places the activity as the only one in the task.

Scaling, performance, and availability decisions on huge infrastructure require a data-driven approach.

• Analyze data on usage, traffic, and resource utilization to identify bottlenecks and areas for improvement.

• Consider the impact of scaling on cost, user experience, and maintenance.

• Implement monitoring and alerting systems to quickly identify and address issues.

• Use load testing and performance profiling to optimize system performance.

• Implement redundancy and failover mechanis...read more

Yes, spell checker is a built-in feature in Microsoft Word.

• Spell checker automatically checks for spelling errors as you type.

• It underlines misspelled words in red and suggests corrections.

• You can also customize the spell checker settings and add words to the dictionary.

• To access the spell checker, go to the Review tab and click on Spelling & Grammar.

• Alternatively, you can use the shortcut key F7 to run the spell checker.

Sort a rotated sorted array in O(n) time without extra space

• Find the index of the minimum element using binary search

• Reverse the two subarrays on either side of the minimum element

• Reverse the entire array

• Example: [4,5,6,7,0,1,2] -> [0,1,2,4,5,6,7]

Test cases for Facebook posts with priorities

• Verify that a user can create a new post

• Check that a user can edit their own post

• Ensure that a user can delete their own post

• Test that a user can like a post

• Verify that a user can comment on a post

Test cases to delete a node from a linked list

• Test deleting the first node in the linked list

• Test deleting a node in the middle of the linked list

• Test deleting the last node in the linked list

• Test deleting a node that does not exist in the linked list

Finding two pairs with a given sum in a BST using O(log n) space.

• Traverse the BST in-order and store the nodes in an array

• Use two pointers approach to find the pairs with the given sum

• Time complexity: O(n), Space complexity: O(log n)

• Optimized approach: Use two stacks to traverse the BST in-order and find the pairs

• Time complexity: O(log n), Space complexity: O(log n)

To select k random numbers from an infinite stream of array with equal probability.

• Use reservoir sampling algorithm to randomly select k numbers from the stream

• Maintain a reservoir array of size k to store the selected numbers

• For each incoming number, generate a random number between 0 and the total count of numbers seen so far

• If the generated number is less than k, replace the corresponding number in the reservoir array with the incoming number

• At the end, the reservoir array...read more

Debugging a full functionality of an API involves thorough testing, logging, and using debugging tools.

• Start by reviewing the API documentation to understand its functionality and expected behavior.

• Write test cases to cover all possible scenarios and edge cases.

• Use logging to track the flow of data and identify any issues.

• Utilize debugging tools like Postman, Swagger, or browser developer tools to inspect API requests and responses.

• Check for error messages and status codes to...read more

Usage history of an application can be analyzed by tracking user actions and behavior.

• Collect data on user interactions with the application

• Analyze the frequency and duration of usage

• Identify patterns and trends in user behavior

• Use data visualization tools to present findings

• Consider user feedback and reviews for additional insights

I would launch a new onboarding experience UI by conducting user research, designing a user-friendly interface, testing with a small group, and gradually rolling out to all users.

• Conduct user research to understand user needs and pain points

• Design a user-friendly interface with clear instructions and intuitive navigation

• Test the new onboarding experience with a small group of users to gather feedback and make improvements

• Gradually roll out the new UI to all users while monito...read more

IPC (Inter-Process Communication) methods in Android allow communication between different processes.

• Binder: Android's default IPC mechanism, provides high-performance communication between processes.

• AIDL (Android Interface Definition Language): Used to define the programming interface for IPC using Binder.

• Intents: Used for asynchronous communication between components within an application or between different applications.

• Content Providers: Allow sharing data between applic...read more

Design a file sharing mechanism between two users

• Use a secure protocol like HTTPS or SFTP

• Implement access control to ensure only authorized users can access the files

• Consider implementing encryption to protect the files during transit and at rest

• Provide a user-friendly interface for uploading and downloading files

• Implement version control to track changes made to the files

• Consider implementing a notification system to alert users of new file uploads or changes

Inorder Traversal can be implemented using recursion or without recursion.

• Inorder Traversal using recursion involves traversing the left subtree, visiting the root node, and then traversing the right subtree.

• Inorder Traversal without recursion involves using a stack to keep track of the nodes to be visited.

• For each node, push it onto the stack and traverse its left subtree until there are no more left nodes.

• Pop the top node from the stack, visit it, and then traverse its righ...read more

Test cases for Amazon Gift Card

• Verify that the gift card balance is correctly displayed

• Test redeeming a gift card code

• Check if multiple gift cards can be applied to a single purchase

• Ensure that expired gift cards are not accepted

• Test the functionality of sending a gift card to someone else

Reverse alternate levels of a binary tree

• Traverse the tree level by level

• Reverse the nodes of alternate levels

• Use a queue or stack to keep track of nodes at each level

• Recursively apply the same process to the children of reversed nodes

LRU cache is a data structure that stores the most recently used items, discarding the least recently used items when full.

• Use a hashmap to store key-value pairs for quick access

• Use a doubly linked list to keep track of the order of items based on their usage

• When an item is accessed, move it to the front of the list

• When the cache is full, remove the least recently used item from the end of the list

Manholes are round because it prevents them from falling into the hole and allows for easy movement of the cover.

• Round covers cannot fall into the hole as they cannot fit through diagonally

• Round covers can be easily moved in any direction

• Round shape distributes weight evenly

• Round shape is easier to manufacture and install

Finding the median of a stream of array in real-time.

• Use two heaps to keep track of the median

• Maintain a max heap for the lower half and a min heap for the upper half

• If the heaps are balanced, the median is the average of the top elements of both heaps

• If the heaps are unbalanced, the median is the top element of the heap with more elements

Find the largest vertical rectangle in an array of strings

• Iterate through each column in the array

• For each column, find the consecutive vertical rectangles of '1's

• Calculate the area of each rectangle and keep track of the largest one

Stay hydrated on the go with our durable and stylish water bottle.

• Highlight the durability of the water bottle

• Emphasize the convenience of staying hydrated while on the go

• Mention the stylish design to appeal to fashion-conscious customers

Protect your laptop in style with our sleek and durable laptop cover.

• Made from high-quality materials to ensure maximum protection

• Available in various sizes to fit different laptop models

• Stylish designs to suit your personal taste

• Easy to clean and maintain for long-lasting use