Free Resources to Learn Each Tech Stack 🧠✨

No excuses. Everything you need is free!

1. Frontend Development
❯ freeCodeCamp.org – HTML, CSS, JS
❯ MDN Web Docs – Best docs for web tech
❯ Frontend Mentor – Real-world challenges
❯ CSS Tricks – CSS deep dives
❯ YouTube: Kevin Powell, Web Dev Simplified

—

2. Backend Development
❯ Node.js Docs
❯ Django Girls Tutorial
❯ The Odin Project – Full Stack
❯ Spring Boot Guides
❯ YouTube: Amigoscode, CodeWithHarry (Hindi), Tech With Tim

—

3. Full-Stack Development
❯ Full Stack Open – React + Node
❯ The Odin Project
❯ CS50 Web – Harvard’s free course
❯ YouTube: Traversy Media, Clever Programmer, JavaScript Mastery

—

4. Data Analytics
❯ Kaggle Learn – Python, SQL, Viz
❯ Maven Analytics – Free Power BI/Tableau projects
❯ Google Data Analytics Course
❯ W3Schools SQL
❯ YouTube: Luke Barousse, Alex The Analyst

—

5. Machine Learning
❯ Google’s ML Crash Course
❯ fast.ai – Deep learning made easy
❯ Kaggle Courses – End-to-end ML
❯ Coursera – Andrew Ng
❯ YouTube: StatQuest, Krish Naik, Codebasics

—

6. DevOps
❯ KodeKloud – Docker, K8s, Ansible
❯ Learn Git Branching
❯ Katacoda – Interactive Linux & DevOps
❯ Roadmap.sh – What to learn
❯ YouTube: TechWorld with Nana, Nana Janashia

Frontend Development Interview Questions

Beginner Level

1. What are semantic HTML tags?
2. Difference between id and class in HTML?
3. What is the Box Model in CSS?
4. Difference between margin and padding?
5. What is a responsive web design?
6. What is the use of the <meta viewport> tag?
7. Difference between inline, block, and inline-block elements?
8. What is the difference between == and === in JavaScript?
9. What are arrow functions in JavaScript?
10. What is DOM and how is it used?

Intermediate Level

1. What are pseudo-classes and pseudo-elements in CSS?
2. How do media queries work in responsive design?
3. Difference between relative, absolute, fixed, and sticky positioning?
4. What is the event loop in JavaScript?
5. Explain closures in JavaScript with an example.
6. What are Promises and how do you handle errors with .catch()?
7. What is a higher-order function?
8. What is the difference between localStorage and sessionStorage?
9. How does this keyword work in different contexts?
10. What is JSX in React?


Advanced Level

1. How does the virtual DOM work in React?
2. What are controlled vs uncontrolled components in React?
3. What is useMemo and when should you use it?
4. How do you optimize a large React app for performance?
5. What are React lifecycle methods (class-based) and their hook equivalents?
6. How does Redux work and when should you use it?
7. What is code splitting and why is it useful?
8. How do you secure a frontend app from XSS attacks?
9. Explain the concept of Server-Side Rendering (SSR) vs Client-Side Rendering (CSR).
10. What are Web Components and how do they work?

React ❤️ for the detailed answers

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𝗧𝗼𝗽 𝟱 𝗧𝗲𝗰𝗵𝗻𝗼𝗹𝗼𝗴𝗶𝗲𝘀 𝗧𝗼 𝗠𝗮𝘀𝘁𝗲𝗿 𝗜𝗻 𝟮𝟬𝟮𝟱 | 𝗘𝗻𝗿𝗼𝗹𝗹 𝗙𝗼𝗿 𝗙𝗥𝗘𝗘 😍 

Acquire industry-relevant skills to grow in your career and stand out to prospective employers.

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Deep Learning with Python

📚 book

𝗪𝗶𝗽𝗿𝗼’𝘀 𝗙𝗿𝗲𝗲 𝗗𝗮𝘁𝗮 𝗦𝗰𝗶𝗲𝗻𝗰𝗲 𝗔𝗰𝗰𝗲𝗹𝗲𝗿𝗮𝘁𝗼𝗿: 𝗬𝗼𝘂𝗿 𝗙𝗮𝘀𝘁-𝗧𝗿𝗮𝗰𝗸 𝘁𝗼 𝗮 𝗗𝗮𝘁𝗮 𝗖𝗮𝗿𝗲𝗲𝗿!😍

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SQL Tricks to Level Up Your Database Skills 🚀

SQL is a powerful language, but mastering a few clever tricks can make your queries faster, cleaner, and more efficient. Here are some cool SQL hacks to boost your skills:

1️⃣ Use COALESCE Instead of CASE
Instead of writing a long CASE statement to handle NULL values, use COALESCE():

SELECT COALESCE(name, 'Unknown') FROM users;

This returns the first non-null value in the list.

2️⃣ Generate Sequential Numbers Without a Table
Need a sequence of numbers but don’t have a numbers table? Use GENERATE_SERIES (PostgreSQL) or WITH RECURSIVE (MySQL 8+):

SELECT generate_series(1, 10);

3️⃣ Find Duplicates Quickly
Easily identify duplicate values with GROUP BY and HAVING:

SELECT email, COUNT(*) 
FROM users 
GROUP BY email 
HAVING COUNT(*) > 1;

4️⃣ Randomly Select Rows
Want a random sample of data? Use:
- PostgreSQL: ORDER BY RANDOM()
- MySQL: ORDER BY RAND()
- SQL Server: ORDER BY NEWID()

5️⃣ Pivot Data Without PIVOT (For Databases Without It)
Use CASE with SUM() to pivot data manually:

SELECT 
    user_id,
    SUM(CASE WHEN status = 'active' THEN 1 ELSE 0 END) AS active_count,
    SUM(CASE WHEN status = 'inactive' THEN 1 ELSE 0 END) AS inactive_count
FROM users
GROUP BY user_id;

6️⃣ Efficiently Get the Last Inserted ID
Instead of running a separate SELECT, use:
- MySQL: SELECT LAST_INSERT_ID();
- PostgreSQL: RETURNING id;
- SQL Server: SELECT SCOPE_IDENTITY();

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What’s the real difference between Junior and Senior Data Analyst?

It’s not just SQL skills or years on the job — it’s how they think.

📚Juniors code right away
🧠Seniors figure out the problem first
Example: Juniors query without asking, Seniors check the goal.

📚Juniors follow orders
🧠Seniors ask questions
Example: Juniors build blindly, Seniors confirm metrics.

📚Juniors patch data
🧠Seniors fix the source
Example: Juniors fill gaps, Seniors debug the ETL.

📚Juniors stall in chaos
🧠Seniors make a plan
Example: Juniors wait, Seniors step up.

📚Juniors focus on tasks
🧠Seniors see the big picture
Example: Juniors report, Seniors connect to goals.

📚Juniors guess
🧠Seniors clarify
Example: Juniors assume, Seniors ask the team.

📚Juniors stick to old tools
🧠Seniors try new ones
Example: Juniors love Excel, Seniors code in Python.

📚Juniors give data
🧠Seniors give insights
Example: Juniors share stats, Seniors spot trends.


Seniority is about mindset, not just time.

𝗛𝗶𝗱𝗱𝗲𝗻 𝗚𝗲𝗺 𝗳𝗼𝗿 𝗙𝗿𝗲𝗲 𝗖𝗼𝘂𝗿𝘀𝗲𝘀 𝗳𝗿𝗼𝗺 𝗠𝗜𝗧, 𝗛𝗮𝗿𝘃𝗮𝗿𝗱 & 𝗦𝘁𝗮𝗻𝗳𝗼𝗿𝗱!😍

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Express.js Learning Roadmap: From Basics to Advanced

1. Getting Started with Express.js

Introduction to Express.js: Understand why Express.js is used and how it simplifies Node.js applications.

Setup: Install Node.js and Express using npm. Create a basic Express server.



2. Core Concepts

Routing: Define routes using app.get(), app.post(), app.put(), and app.delete().

Middleware: Understand middleware functions and use built-in, third-party, and custom middleware.

Request and Response: Handle HTTP requests (req) and responses (res).



3. Templating Engines

Introduction: Learn about templating engines like EJS, Handlebars, or Pug.

Dynamic HTML: Render dynamic content using templates.



4. Working with RESTful APIs

Create APIs: Build RESTful APIs with Express.

Handle Query Parameters: Parse URL parameters and query strings.

Send JSON Responses: Format and send JSON data to clients.



5. Middleware and Error Handling

Middleware Basics: Use next() for request flow.

Error Handling: Implement custom error-handling middleware.

Logging: Use libraries like morgan for logging requests.



6. Database Integration

Connect to Databases: Integrate MongoDB (Mongoose), MySQL, or PostgreSQL.

Perform CRUD Operations: Build database-backed routes for Create, Read, Update, Delete operations.



7. Authentication and Authorization

Authentication: Implement user authentication using sessions, cookies, or JSON Web Tokens (JWT).

Authorization: Restrict routes to specific user roles.


8. File Uploads and Static Files

File Uploads: Use multer for handling file uploads.

Serve Static Files: Use express.static() to serve images, CSS, and JavaScript files.



9. Advanced Features

CORS: Enable Cross-Origin Resource Sharing for APIs.

Rate Limiting: Protect APIs from abuse using rate-limiting middleware.

Real-Time Features: Integrate with WebSockets for live data.



10. Testing and Debugging

Unit Testing: Test routes using supertest and Jest or Mocha.

Debugging: Use tools like node-inspect or debug library.


11. Deployment

Prepare for Deployment: Use environment variables and production-ready configurations.

Deployment Platforms: Deploy on Heroku, Vercel, or AWS Elastic Beanstalk.

Scaling: Optimize your app for performance and scalability.


12. Build Projects

Beginner: Build a to-do list API.

Intermediate: Develop a blog backend with user authentication.

Advanced: Create a real-time chat application using Express and WebSockets.

Deploy your projects to demonstrate your skills.

📂 Web Development Resources

ENJOY LEARNING 👍👍

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Complete roadmap to learn Python and Data Structures & Algorithms (DSA) in 2 months

### Week 1: Introduction to Python

Day 1-2: Basics of Python
- Python setup (installation and IDE setup)
- Basic syntax, variables, and data types
- Operators and expressions

Day 3-4: Control Structures
- Conditional statements (if, elif, else)
- Loops (for, while)

Day 5-6: Functions and Modules
- Function definitions, parameters, and return values
- Built-in functions and importing modules

Day 7: Practice Day
- Solve basic problems on platforms like HackerRank or LeetCode

### Week 2: Advanced Python Concepts

Day 8-9: Data Structures in Python
- Lists, tuples, sets, and dictionaries
- List comprehensions and generator expressions

Day 10-11: Strings and File I/O
- String manipulation and methods
- Reading from and writing to files

Day 12-13: Object-Oriented Programming (OOP)
- Classes and objects
- Inheritance, polymorphism, encapsulation

Day 14: Practice Day
- Solve intermediate problems on coding platforms

### Week 3: Introduction to Data Structures

Day 15-16: Arrays and Linked Lists
- Understanding arrays and their operations
- Singly and doubly linked lists

Day 17-18: Stacks and Queues
- Implementation and applications of stacks
- Implementation and applications of queues

Day 19-20: Recursion
- Basics of recursion and solving problems using recursion
- Recursive vs iterative solutions

Day 21: Practice Day
- Solve problems related to arrays, linked lists, stacks, and queues

### Week 4: Fundamental Algorithms

Day 22-23: Sorting Algorithms
- Bubble sort, selection sort, insertion sort
- Merge sort and quicksort

Day 24-25: Searching Algorithms
- Linear search and binary search
- Applications and complexity analysis

Day 26-27: Hashing
- Hash tables and hash functions
- Collision resolution techniques

Day 28: Practice Day
- Solve problems on sorting, searching, and hashing

### Week 5: Advanced Data Structures

Day 29-30: Trees
- Binary trees, binary search trees (BST)
- Tree traversals (in-order, pre-order, post-order)

Day 31-32: Heaps and Priority Queues
- Understanding heaps (min-heap, max-heap)
- Implementing priority queues using heaps

Day 33-34: Graphs
- Representation of graphs (adjacency matrix, adjacency list)
- Depth-first search (DFS) and breadth-first search (BFS)

Day 35: Practice Day
- Solve problems on trees, heaps, and graphs

### Week 6: Advanced Algorithms

Day 36-37: Dynamic Programming
- Introduction to dynamic programming
- Solving common DP problems (e.g., Fibonacci, knapsack)

Day 38-39: Greedy Algorithms
- Understanding greedy strategy
- Solving problems using greedy algorithms

Day 40-41: Graph Algorithms
- Dijkstra’s algorithm for shortest path
- Kruskal’s and Prim’s algorithms for minimum spanning tree

Day 42: Practice Day
- Solve problems on dynamic programming, greedy algorithms, and advanced graph algorithms

### Week 7: Problem Solving and Optimization

Day 43-44: Problem-Solving Techniques
- Backtracking, bit manipulation, and combinatorial problems

Day 45-46: Practice Competitive Programming
- Participate in contests on platforms like Codeforces or CodeChef

Day 47-48: Mock Interviews and Coding Challenges
- Simulate technical interviews
- Focus on time management and optimization

Day 49: Review and Revise
- Go through notes and previously solved problems
- Identify weak areas and work on them

### Week 8: Final Stretch and Project

Day 50-52: Build a Project
- Use your knowledge to build a substantial project in Python involving DSA concepts

Day 53-54: Code Review and Testing
- Refactor your project code
- Write tests for your project

Day 55-56: Final Practice
- Solve problems from previous contests or new challenging problems

Day 57-58: Documentation and Presentation
- Document your project and prepare a presentation or a detailed report

Day 59-60: Reflection and Future Plan
- Reflect on what you've learned
- Plan your next steps (advanced topics, more projects, etc.)

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SQL table interview questions:

1. What is a DUAL table and why do we need it?
- it is a special table which gets created automatically when we install Oracle database. It can be used to select pseudo columns, perform calculations and also as sequence generator etc.

2. How many columns and rows are present in DUAL table?
- one column & one row by default.

3. Can we insert more rows in to DUAL table?
- Yes.

4. What's the easiest way to backup a table / how can we create a table based on existing table?
- CREATE TABLE SALES_COPY AS SELECT * FROM SALES.

5. Can we drop all the columns from a table?
- No.

6. What is the difference between count(1) and count(*)?
- Both are same. Both consume same amount of resources, Both perform same operation

𝗟𝗮𝘂𝗻𝗰𝗵 𝗬𝗼𝘂𝗿 𝗧𝗲𝗰𝗵 𝗖𝗮𝗿𝗲𝗲𝗿 𝗶𝗻 𝟮𝟬𝟮𝟱 — 𝗪𝗶𝘁𝗵 𝗠𝗶𝗰𝗿𝗼𝘀𝗼𝗳𝘁’𝘀 𝗙𝗿𝗲𝗲 𝗟𝗲𝗮𝗿𝗻𝗶𝗻𝗴 𝗣𝗮𝘁𝗵𝘀!😍

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5 Algorithms you must know as a data scientist 👩‍💻 🧑‍💻

1. Dimensionality Reduction
- PCA, t-SNE, LDA

2. Regression models
- Linesr regression, Kernel-based regression models, Lasso Regression, Ridge regression, Elastic-net regression

3. Classification models
- Binary classification- Logistic regression, SVM
- Multiclass classification- One versus one, one versus many
- Multilabel classification

4. Clustering models
- K Means clustering, Hierarchical clustering, DBSCAN, BIRCH models

5. Decision tree based models
- CART model, ensemble models(XGBoost, LightGBM, CatBoost)

Best Data Science & Machine Learning Resources: https://topmate.io/coding/914624

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1: How would you preprocess and tokenize text data from tweets for sentiment analysis? Discuss potential challenges and solutions.

- Answer: Preprocessing and tokenizing text data for sentiment analysis involves tasks like lowercasing, removing stop words, and stemming or lemmatization. Handling challenges like handling emojis, slang, and noisy text is crucial. Tools like NLTK or spaCy can assist in these tasks.


2: Explain the collaborative filtering approach in building recommendation systems. How might Twitter use this to enhance user experience?

- Answer: Collaborative filtering recommends items based on user preferences and similarities. Techniques include user-based or item-based collaborative filtering and matrix factorization. Twitter could leverage user interactions to recommend tweets, users, or topics.


3: Write a Python or Scala function to count the frequency of hashtags in a given collection of tweets.

- Answer (Python):

     def count_hashtags(tweet_collection):
         hashtags_count = {}
         for tweet in tweet_collection:
             hashtags = [word for word in tweet.split() if word.startswith('#')]
             for hashtag in hashtags:
                 hashtags_count[hashtag] = hashtags_count.get(hashtag, 0) + 1
         return hashtags_count
     

4: How does graph analysis contribute to understanding user interactions and content propagation on Twitter? Provide a specific use case.

- Answer: Graph analysis on Twitter involves examining user interactions. For instance, identifying influential users or detecting communities based on retweet or mention networks. Algorithms like PageRank or Louvain Modularity can aid in these analyses.

📚40 Windows Command Prompt commands you need to know📚

1. ipconfig
2. ipconfig /all
3. findstr
4. ipconfig /release
5. ipconfig /renew
6. ipconfig /displaydns
7. clip
8. ipconfig /flushdns
9. nslookup
10. cls
11. getmac /v
12. powercfg /energy
13. powercfg /batteryreport
14. assoc
15. chkdsk /f
16. chkdsk /r
17. Follow Coding Army
17. sfc /scannow
18. DISM /Online /Cleanup /CheckHealth
19. DISM /Online /Cleanup /ScanHealth
20. DISM /Online /Cleanup /RestoreHealth
21. tasklist
22. taskkill
23. netsh wlan show wlanreport
24. netsh interface show interface
25. netsh interface ip show address | findstr "IP Address"
26. netsh interface ip show dnsservers
27. netsh advfirewall set allprofiles state off
28. netsh advfirewall set allprofiles state on
29. ping
30. ping -t
31. tracert
32. tracert -d
33. netstat
34. netstat -af
35. netstat -o
36. netstat -e -t 5
37. route print
38. route add
39. route delete
40. shutdown /r /fw /f /t 0

Command 40:
*Details:*
The command shutdown /r/fw/f/t 0 restarts the computer immediately and forces it to boot directly into the BIOS or UEFI firmware settings, bypassing the normal Windows startup process. It's a convenient way to access your firmware settings without having to repeatedly press a specific key during startup (like Del, F2, F10, F12, Esc, etc., which vary depending on the motherboard manufacturer.

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