Collekto Interview Questions and Answers

Find the subset of an array with the largest sum of continuous positive numbers.

• Iterate through the array and keep track of the current sum and the maximum sum seen so far.

• If the current element is positive, add it to the current sum. If it is negative, reset the current sum to 0.

• Also keep track of the start and end indices of the maximum sum subset.

• Return the subset using the start and end indices.

Find smallest substring in s1 containing all characters of s2.

• Create a hash table of characters in s2

• Use sliding window technique to find smallest substring in s1

• Check if all characters in s2 are present in the substring

• Update the smallest substring if a smaller one is found

Algorithm to reverse a linked list

• Create a new empty linked list

• Traverse the original linked list and insert each node at the beginning of the new list

• Return the new list

Lazy loading is a technique used to defer the loading of non-critical resources until they are needed.

• Advantages: faster initial page load, reduced bandwidth usage, improved user experience

• Disadvantages: increased complexity, potential for slower subsequent page loads, difficulty with SEO

• Examples: images, videos, and other media files can be loaded only when they are visible on the screen

Ajax is a technique for creating fast and dynamic web pages. AngularJS is a framework for building dynamic web applications, while jQuery is a library for simplifying HTML DOM traversal and manipulation.

• Ajax stands for Asynchronous JavaScript and XML

• It allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes

• AngularJS is a JavaScript framework that extends HTML with new attrib...read more

A traffic light system controls the flow of traffic at intersections.

• The system consists of three lights: red, yellow, and green.

• Each light has a specific duration for which it stays on.

• The system also includes sensors to detect the presence of vehicles and pedestrians.

• The duration of each light can be adjusted based on traffic patterns.

• The system can be connected to a central control system for remote monitoring and m

Indexes in MySQL are used to improve query performance by allowing faster data retrieval.

• Indexes are created on one or more columns of a table.

• They work by creating a separate data structure that allows for faster data retrieval.

• Indexes can be created using the CREATE INDEX statement.

• Indexes can also be dropped using the DROP INDEX statement.

• Indexes can be used to speed up SELECT, UPDATE, and DELETE statements.

• Indexes ...read more

include_once and require_once are PHP functions used to include files. The difference is in how they handle errors.

• include_once will only include the file once, and will not throw a fatal error if the file is not found

• require_once will also only include the file once, but will throw a fatal error if the file is not found

• Both functions are used to include files that contain functions or variables that are needed in the

Sessions and cookies are both used for maintaining user state, but sessions are server-side and cookies are client-side.

• Sessions store user data on the server, while cookies store data on the client's browser

• Sessions are more secure than cookies because the data is not accessible to the client

• Cookies can be used for tracking user behavior and preferences

• Sessions are typically used for authentication and authorization p...read more

To find missing number in an array of first n numbers.

• Calculate the sum of first n numbers using formula n*(n+1)/2

• Calculate the sum of given array using loop

• Subtract the sum of array from sum of first n numbers to get the missing number

Design a database schema for a chat application with individual and group messaging.

• Create a 'users' table with unique user IDs

• Create a 'messages' table with message IDs, sender and receiver IDs, message content, and timestamp

• Create a 'groups' table with unique group IDs and group names

• Create a 'group_members' table with group ID and user ID to track group membership

• Use foreign keys to link tables together

• Consider inde

SQL query to retrieve all unread messages upon user sign in

• Use a JOIN statement to combine the messages and user tables

• Filter the results to only show messages that have not been read by the user

• Use the user's sign in information to identify which messages are unread

I am excited to join OLX because of its innovative approach to online marketplaces and its commitment to customer satisfaction.

• I am impressed by OLX's user-friendly platform and its ability to connect buyers and sellers from all over the world.

• I am excited to work with a team of talented developers who are passionate about creating cutting-edge technology.

• I believe that OLX's focus on customer satisfaction aligns with ...read more

I have faced difficulties in debugging complex code and managing project timelines.

• Debugging complex code with multiple dependencies

• Managing project timelines with changing requirements

• Working with legacy code and outdated technologies

• Collaborating with team members in different time zones

• Dealing with unexpected bugs and errors

I report to the Technical Lead and am part of the development team.

• I report to the Technical Lead

• I am part of the development team

Our website receives an average of 10,000 unique visitors per day.

• Our website has a steady flow of traffic with a consistent number of unique visitors per day.

• We use Google Analytics to track our web traffic and analyze user behavior.

• Our peak traffic times are during weekdays from 9am to 5pm.

• We have noticed an increase in mobile traffic over the past year.

• Our website's traffic is primarily driven by organic search and

Implementing a shuffle function for a playlist of songs

• Create a new empty playlist

• Randomly select a song from the original playlist and add it to the new playlist

• Remove the selected song from the original playlist

• Repeat until all songs have been added to the new playlist

• Return the new shuffled playlist

Memory leak is a situation where a program fails to release memory it no longer needs.

• Memory leaks can cause a program to consume more and more memory over time, eventually leading to crashes or other issues.

• Memory leaks can be caused by programming errors such as not freeing memory after it is no longer needed.

• Tools like valgrind can be used to detect memory leaks in C and C++ programs.

• Examples of memory leaks include...read more

Arrays have fixed size and can lead to memory wastage and performance issues.

• Arrays have a fixed size and cannot be resized dynamically.

• Inserting or deleting elements in an array can be time-consuming.

• Arrays can lead to memory wastage if they are not fully utilized.

• Arrays can cause performance issues if they are too large and need to be traversed frequently.

• Arrays can also be prone to buffer overflow attacks.

• Example: A...read more

Function to hide text on mouse click in JavaScript

• Create a function that takes an element as input

• Add an event listener to the element for a mouse click

• Toggle the element's display property between 'none' and its original value

Find two elements in an unsorted array whose sum is equal to a given number x.

• Use a hash table to store the difference between x and each element in the array.

• Iterate through the array and check if the current element is in the hash table.

• Return the pair of elements that add up to x.

BST stands for Binary Search Tree, a data structure used for efficient searching and sorting operations.

• BST is a tree-like data structure where each node has at most two children.

• The left child of a node contains a value less than the parent node, while the right child contains a value greater than the parent node.

• BST allows for efficient searching and sorting operations with a time complexity of O(log n).

• Examples of a...read more

Number of possible BSTs with 2 and 3 nodes.

• For 2 nodes, only 2 BSTs are possible.

• For 3 nodes, 5 BSTs are possible.

• Number of BSTs can be calculated using Catalan numbers formula.

• Catalan(2) = 2, Catalan(3) = 5.

Answering the question about possible trees with two and three nodes.

• For two nodes, there is only one possible tree.

• For three nodes, there are three possible trees.

• The formula for calculating the number of possible trees with n nodes is (2n-3)!!.

• The double exclamation mark represents the double factorial function.

• The double factorial function is defined as n!! = n(n-2)(n-4)...(1 or 2).

B+ trees are balanced trees used for indexing and searching large amounts of data.

• B+ trees are similar to binary search trees but have multiple keys per node.

• They are commonly used in databases and file systems.

• B+ trees have a high fanout, reducing the number of disk accesses required for searching.

• They are also self-balancing, ensuring efficient performance even with large amounts of data.

• Example: In a database, a B+ ...read more

Yes, I have a few questions.

• Can you tell me more about the team I'll be working with?

• What is the company culture like?

• What are the biggest challenges the team is currently facing?

• Can you walk me through the development process for a typical project?

• What opportunities are there for professional growth and development?

I prefer hash tables for their constant time lookup and insertion.

• Hash tables are efficient for storing and retrieving data.

• They have constant time complexity for both insertion and lookup.

• They can be implemented using arrays or linked lists.

• Examples include Python's dictionary and Java's HashMap.

Yes, we can implement a stack using two queues.

• Push operation: Enqueue the element to the first queue.

• Pop operation: Dequeue all elements from the first queue and enqueue them to the second queue until the last element. Dequeue and return the last element. Swap the names of the queues.

• Top operation: Same as pop operation but don't dequeue the last element.

• Example: Push 1, 2, 3. Queue 1: 1 2 3. Queue 2: empty. Pop opera...read more

Find minimum no of platforms required to avoid collision between trains based on their arrival and departure times.

• Sort both arrays in ascending order

• Initialize platform count and max count to 1

• Loop through both arrays and compare arrival and departure times

• If arrival time is less than or equal to departure time, increment platform count

• Else, decrement platform count

• Update max count if platform count is greater than ma

JVM stands for Java Virtual Machine. It is an abstract machine that provides a runtime environment for Java programs.

• JVM is responsible for interpreting the compiled Java code and executing it.

• It provides platform independence by converting bytecode into machine-specific code.

• JVM has various components like class loader, bytecode verifier, and execution engine.

• Compiler converts source code into bytecode, while JVM exec...read more

I am a software engineer with experience in developing web applications and a passion for learning new technologies.

• Experienced in developing web applications using technologies such as Java, Spring, and Angular

• Passionate about learning new technologies and keeping up with industry trends

• Strong problem-solving skills and ability to work in a team environment

• Completed a Bachelor's degree in Computer Science from XYZ Uni

PayTM is an Indian e-commerce payment system and digital wallet company.

• PayTM was founded in 2010 by Vijay Shekhar Sharma.

• It started as a mobile recharge and bill payment platform.

• PayTM has expanded to offer services like online shopping, movie ticket booking, and travel bookings.

• It also offers a digital wallet that can be used to pay for various services and products.

• PayTM has over 350 million registered users and is ...read more

I would like to add a feature for splitting bills among friends.

• The feature would allow users to split bills for movies, dinners, etc.

• Users can select friends from their contact list and split the bill equally or unequally.

• The app would send a notification to the selected friends to pay their share.

• The feature would make it easier for users to split expenses and avoid awkward conversations.

• It would also encourage more

My favourite app is Spotify. I would like to see improvements in the algorithm for personalized playlists.

• Improved algorithm for personalized playlists

• Better integration with social media platforms

• Option to create collaborative playlists with friends

My favourite subject is Computer Science.

• I enjoy programming and problem-solving.

• I find algorithms and data structures fascinating.

• I am interested in artificial intelligence and machine learning.

• I like learning about new technologies and keeping up with industry trends.

I choose NIT Hamirpur because of its excellent academic reputation and beautiful campus.

• NIT Hamirpur has a strong focus on academics and research, which aligns with my career goals.

• The campus is located in a serene and picturesque location, which provides a conducive environment for learning.

• The faculty members are highly experienced and knowledgeable, and are always willing to help students.

• The college has state-of-th...read more

Find the odd repeating element from an array of strings

• Use a hash table to count the frequency of each element

• Iterate through the hash table to find the element with an odd count

Finding an element in a sorted 2D matrix

• Start from the top right corner or bottom left corner

• Compare the target element with the current element

• Move left or down if the target is smaller, else move right or up

• Repeat until the target is found or all elements are checked

SQL query to find Nth highest salary from table

• Use ORDER BY and LIMIT clauses

• Use subquery to get the Nth highest salary

• Handle cases where there are less than N distinct salaries

Function to swap '3' and '4' without using if-else

• Use XOR operator to swap the values

• Convert the input to ASCII code and perform the swap

• Use a lookup table to map the values

I am a software developer with experience in Java and Python.

• Proficient in Java and Python programming languages

• Experience in developing web applications using Spring framework

• Familiarity with database management systems like MySQL and MongoDB

PAYTM is a leading digital payment platform in India with a wide range of services.

• PAYTM has a user-friendly interface and offers a seamless payment experience.

• It provides a variety of services like mobile recharges, bill payments, and online shopping.

• PAYTM has a strong focus on security and fraud prevention measures.

• It has a large user base and is widely accepted by merchants across India.

• PAYTM is constantly innovatin...read more

Yes, I am open to pursuing further studies in the future.

• I believe in continuous learning and staying updated with the latest technologies.

• Further studies can help me specialize in a particular field and enhance my skills.

• I may consider pursuing a master's degree in computer science or a related field.

• However, my immediate focus is on gaining practical experience and contributing to the organization.

PAYTM grew fast due to its innovative approach and early adoption of digital payments.

• Early adoption of digital payments in India

• Innovative approach with features like mobile recharges, bill payments, and cashback offers

• Expansion into e-commerce and financial services

• Strategic partnerships with major companies like Uber and Alibaba