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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 ...
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...
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 ...
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
I appeared for an interview before Dec 2020.
Round duration - 60 Minutes
Round difficulty - Medium
This was a Data Structures and Algorithms round with preety good questions . I was expected to come up with an efficient approach and code it as well .
Your house is located at the origin (0,0) of a 2-D plane. There are N
neighbors living at different points on the plane. Your goal is to visit exactly K
neighb...
Find the K closest points to the origin in a 2-D plane using Euclidean Distance.
Calculate the Euclidean Distance of each point from the origin
Sort the points based on their distances
Return the first K points as the closest neighbors
Given a sorted array of 'N' integers, your task is to generate the power set for this array. Each subset of this power set should be individually sorted.
A power set of a set 'ARR' i...
Generate the power set of a sorted array of integers with individually sorted subsets.
Use recursion to generate all possible subsets by including or excluding each element in the array.
Sort each subset before adding it to the power set.
Handle base cases for empty array and single element array.
Ensure the subsets are unique by using a set data structure.
Time complexity can be exponential due to the nature of generating
Round duration - 50 Minutes
Round difficulty - Hard
This was also a DSA round where I was asked to code only one of the questions but I eventually ended up coding both as I had some spare time and explained my approches very smoothly to the interviewer . This round went preety well .
Convert a string representing a Roman numeral into its integer equivalent and return the result.
Roman numerals are represented by seven different symbol...
Convert a Roman numeral string to its integer equivalent.
Create a mapping of Roman numeral symbols to their integer values.
Iterate through the input string and add the corresponding integer values.
Handle cases where subtraction is needed (e.g., IV = 4, IX = 9).
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Find pairs of elements in an array that sum up to a given value, sorted in a specific order.
Iterate through the array and for each element, check if the complement (S - current element) exists in a hash set.
If the complement exists, add the pair to the result list.
Sort the result list based on the criteria mentioned in the question.
Return the sorted list of pairs.
Round duration - 50 Minutes
Round difficulty - Medium
This was also a DSA round with 2 questions . One was implementation heavy and the other was related to recursion and so I handled it carefully so that my code does not run into TLE or Segmentation Fault.
You are provided with a string expression
consisting of characters '+', '-', '*', '/', '(', ')' and digits '0' to '9', representing an arithmetic express...
Evaluate arithmetic expressions in infix notation with given operators and precedence rules.
Parse the infix expression to postfix using a stack.
Evaluate the postfix expression using a stack.
Handle operator precedence and parentheses while evaluating.
Ensure no division by zero cases and operands fit in 32-bit integer.
You are given a sorted integer array ARR
of size N
. Your task is to remove the duplicates in such a way that each element appears only once. The outpu...
Remove duplicates from a sorted array in-place with O(1) extra memory.
Use two pointers - one for iterating through the array and another for placing unique elements.
Compare current element with next element to identify duplicates and skip them.
Update array in-place by moving unique elements to the front.
Return the length of the array after removal of duplicates.
Round duration - 50 Minutes
Round difficulty - Medium
This was a typical System Design round where I was asked about the various features of Facebook and what sort of data structures and algorithms are used in implementing them .
Facebook stores likes and dislikes using a combination of databases and algorithms.
Likes and dislikes are stored in databases such as MySQL or Cassandra.
Algorithms are used to analyze user behavior and recommend content based on likes and dislikes.
User interactions with posts, pages, and ads are tracked to determine likes and dislikes.
Likes and dislikes may also be used to personalize the user's feed and target ads mor
Facebook implements graph search using a graph database to efficiently search for connections between users and their interests.
Facebook uses a graph database to store connections between users, pages, groups, etc.
The graph search algorithm traverses the graph to find relevant connections based on user queries.
It takes into account factors like user relationships, interests, and interactions to provide personalized sea
Round duration - 50 Minutes
Round difficulty - Medium
This was a preety intense round as I was grilled more on my System Design concepts but eventually I was able to asnwers all the questions with some help from the interviewer.
Hadoop is a framework for distributed storage and processing of large data sets.
Hadoop is used for storing and processing big data across a distributed network of computers.
It is based on the MapReduce programming model, which allows for parallel processing of data.
Hadoop consists of HDFS for storage and YARN for resource management.
It is used for tasks like data warehousing, log processing, recommendation systems, and...
Facebook Chat works by using a combination of websockets, long polling, and push technology to deliver real-time messaging.
Facebook Chat uses websockets for real-time communication between the client and server.
Long polling is used to check for new messages when websockets are not supported.
Push technology is used to notify users of new messages even when the chat window is not open.
Messages are stored in a database an...
Tip 1 : Must do Previously asked Interview as well as Online Test Questions.
Tip 2 : Go through all the previous interview experiences from Codestudio and Leetcode.
Tip 3 : Do at-least 2 good projects and you must know every bit of them.
Tip 1 : Have at-least 2 good projects explained in short with all important points covered.
Tip 2 : Every skill must be mentioned.
Tip 3 : Focus on skills, projects and experiences more.
I appeared for an interview before Mar 2021.
Round duration - 60 minutes
Round difficulty - Medium
This was a 1 hour online coding round on hackerrank platform. 3 DSA questions were given.
Given the stock prices for 'N' days, your goal is to determine the maximum profit that can be achieved. You can buy and sell the stocks any number of times but can onl...
The goal is to determine the maximum profit that can be achieved by buying and selling stocks on different days.
Iterate through the stock prices and buy on days when the price is lower than the next day, and sell on days when the price is higher than the next day.
Calculate the profit by summing up the differences between buying and selling prices.
Repeat the process for each test case and output the maximum profit possi
Every day, Ninja dreams of a number but does not understand its significance. Upon investigation, Ninja discovers that converting this number to binary, taking its com...
Convert a number to binary, take its complement, and convert back to decimal.
Convert the given number to binary representation
Take the complement of the binary number by swapping '1's and '0's
Convert the complement back to decimal representation
Return the complement number for each test case
You are given an array arr
consisting of N
integers. Construct a number from these integers such that, for each bit position, if the quantity of set bits (1s) is greater tha...
Generate a number based on majority set bits in given integers array.
Iterate through each bit position and count set and unset bits
Construct the resulting number based on majority set bits at each position
Return the final constructed number
Round duration - 60 minutes
Round difficulty - Easy
In this round, a DSA question was first asked. Then a lot of discussion regarding the various test cases around this question took place. (e.g, handing of -ve numbers , decimals , overflow etc).
Main concentration was just to get as many as test cases possible and an efficient solution as well.
And Some common question like why you coding in C++?
Given an integer 'N', continue summing its digits until the result is a single-digit number. Your task is to determine the final value of 'N' after applying this operation ...
Given an integer, sum its digits until a single-digit number is obtained.
Iteratively sum the digits of the integer until a single-digit number is reached
Output the final single-digit integer for each test case
Handle multiple test cases efficiently
OOP allows for code reusability, modularity, and easier maintenance.
Encapsulation: Bundling data and methods together to protect data from outside interference.
Inheritance: Allows for the creation of new classes based on existing classes, promoting code reuse.
Polymorphism: Objects can be treated as instances of their parent class, allowing for flexibility and extensibility.
Modularity: Breaking down a program into small...
Round duration - 60 minutes
Round difficulty - Easy
Again one coding question to be done on shared screen
Given two graphs – a directed graph DIR_GRAPH
and an undirected graph UNDIR_GRAPH
– you are tasked with counting the number of triangles in each of the graphs.
In t...
Count the number of triangles in a directed and undirected graph.
Parse the input to extract vertices, edges, and edges between vertices.
Implement a function to count triangles in both directed and undirected graphs.
Return the counts of triangles for each test case.
Tip 1 : Must do Previously asked Interview as well as Online Test Questions.
Tip 2 : Go through all the previous interview experiences from Codestudio and Leetcode.
Tip 3 : Do at-least 2 good projects and you must know every bit of them.
Tip 1 : Have at-least 2 good projects explained in short with all important points covered.
Tip 2 : Every skill must be mentioned.
Tip 3 : Focus on skills, projects and experiences more.
I appeared for an interview before Mar 2021.
Round duration - 60 minutes
Round difficulty - Easy
Technical Interview round with questions based on DSA, UNIX commands , Web Security etc.
You are provided with an array nums
which contains the first N positive integers. In this array, one integer appears twice, and one integer is missi...
Identify the repeating and missing number in an array of first N positive integers.
Iterate through the array and keep track of the sum of elements and sum of squares to find the missing and repeating numbers.
Use a set to identify the repeating number and calculate the missing number using the sum formula.
Handle multiple test cases by looping through each case and applying the same logic.
Example: For nums = [1, 2, 3, 4,...
ps displays a snapshot of current processes, while top provides real-time information and allows for interactive management.
ps displays a static list of processes, while top continuously updates the list
top allows for interactive management of processes (e.g. killing, renicing), while ps does not
ps is useful for a quick snapshot of processes, while top is useful for monitoring real-time system activity
Cross-site scripting (XSS) is a type of security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users.
XSS occurs when a web application allows users to input unvalidated data that is then displayed on the page without proper encoding.
There are three main types of XSS: stored XSS, reflected XSS, and DOM-based XSS.
An example of XSS is when a user inputs a script into a sear...
Prevent SQL injection by using parameterized queries, input validation, and escaping user input.
Use parameterized queries to separate SQL code from user input.
Validate and sanitize user input to prevent malicious code injection.
Escape special characters in user input before executing SQL queries.
The command to kill all running Java processes is 'pkill -f java'
Use the 'pkill' command followed by the '-f' flag and 'java' keyword to kill all Java processes
Be cautious when using this command as it will terminate all running Java processes
Make sure to have the necessary permissions to kill processes on the system
Round duration - 60 minutes
Round difficulty - Medium
Questions based on designing. My first project as it was related to Image processing, so he also asked questions related to it.
Design a system for a traffic enforcement camera.
1. Install cameras at strategic locations to monitor traffic violations.
2. Use image recognition software to detect violations such as speeding or running red lights.
3. Store captured images and violation data in a secure database.
4. Generate automated tickets and send them to violators.
5. Implement a user interface for law enforcement to review violations and approve ti
JSON is a lightweight data interchange format that is easy for humans to read and write and easy for machines to parse and generate.
JSON is based on key-value pairs, where keys are always strings enclosed in double quotes.
Data is organized in a hierarchical structure using objects and arrays.
Example: {"name": "John", "age": 30}
Example: [{"name": "Alice", "age": 25}, {"name": "Bob", "age": 35}]
I am familiar with testing frameworks such as JUnit, Selenium, and TestNG.
JUnit
Selenium
TestNG
The best protocol for storing images is JPEG (Joint Photographic Experts Group).
JPEG is a widely used format for storing images due to its high compression ratio and good image quality.
It supports millions of colors and is compatible with most devices and software.
Other options include PNG (Portable Network Graphics) for lossless compression and GIF (Graphics Interchange Format) for animations.
Round duration - 30 minutes
Round difficulty - Easy
This was a typical HR round with questions related to my final year project and some behavioral problems.
Tip 1 : Must do Previously asked Interview as well as Online Test Questions.
Tip 2 : Go through all the previous interview experiences from Codestudio and Leetcode.
Tip 3 : Do at-least 2 good projects and you must know every bit of them.
Tip 1 : Have at-least 2 good projects explained in short with all important points covered.
Tip 2 : Every skill must be mentioned.
Tip 3 : Focus on skills, projects and experiences more.
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