Телеграм канал «CRACKING the CODING INTERVIEW»

FREE Resources to Learn Artificial Intelligence 🔥

* Python – python.org/doc
* Math for AI – khanacademy.org/math/statistics‑probability
* Machine Learning – scikit‑learn.org/stable
* Deep Learning – pytorch.org/tutorials
* Generative AI – google.com/ai/learn‑ai‑skills
* NLP (Natural Language Processing) – huggingface.co/learn/nlp‑course
* Reinforcement Learning – openai.com/research
* AI Ethics – resourcelist.ai/ai‑ethics
* AI Research – paperswithcode.com
* AI Projects – kaggle.com/learn/ai
* AI Learning Hub – learn.microsoft.com/en‑us/ai
* GitHub AI List – github.com/mrsaeeddev/free‑ai‑resources

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🌐 Frontend Development Concepts You Should Know

Frontend development focuses on building the user interface (UI) of websites and web applications—the part users see and interact with in the browser. It combines design, structure, interactivity, and performance to create responsive and user-friendly web experiences.

1️⃣ Core Technologies of Frontend Development

Frontend development is built on three foundational technologies:
- HTML (HyperText Markup Language): provides the structure of a webpage
- CSS (Cascading Style Sheets): controls the visual appearance and layout
- JavaScript: adds interactivity and dynamic behavior to web pages

2️⃣ Important Frontend Concepts

- Responsive Design: ensures websites work properly across devices
- DOM (Document Object Model): represents the structure of a webpage as objects
- Event Handling: frontend applications respond to user actions
- Asynchronous Programming: fetch data without reloading pages

3️⃣ Frontend Frameworks & Libraries

- React: popular JavaScript library for building component-based UI
- Angular: full frontend framework for large-scale applications
- Vue.js: lightweight framework known for simplicity and flexibility

4️⃣ Styling Tools

- CSS Frameworks: Tailwind CSS, Bootstrap, Material UI
- CSS Preprocessors: Sass, Less

5️⃣ Frontend Development Tools

- VS Code: code editor
- Git: version control
- Webpack / Vite: module bundlers
- NPM / Yarn: package managers
- Chrome DevTools: debugging

6️⃣ Performance Optimization

- lazy loading
- code splitting
- image optimization
- caching strategies
- minimizing HTTP requests

7️⃣ Typical Frontend Development Workflow

1. UI/UX Design
2. HTML Structure
3. Styling with CSS
4. Add JavaScript Interactivity
5. Integrate APIs
6. Test and debug
7. Deploy application

8️⃣ Real-World Frontend Projects

- Responsive Portfolio Website
- Weather App
- To-Do List Application
- E-commerce Product Page
- Dashboard UI

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SQL From Basic to Advanced level

Basic SQL is ONLY 7 commands:
- SELECT
- FROM
- WHERE (also use SQL comparison operators such as =, <=, >=, <> etc.)
- ORDER BY
- Aggregate functions such as SUM, AVERAGE, COUNT etc.
- GROUP BY
- CREATE, INSERT, DELETE, etc.
You can do all this in just one morning.

Once you know these, take the next step and learn commands like:
- LEFT JOIN
- INNER JOIN
- LIKE
- IN
- CASE WHEN
- HAVING (undertstand how it's different from GROUP BY)
- UNION ALL
This should take another day.

Once both basic and intermediate are done, start learning more advanced SQL concepts such as:
- Subqueries (when to use subqueries vs CTE?)
- CTEs (WITH AS)
- Stored Procedures
- Triggers
- Window functions (LEAD, LAG, PARTITION BY, RANK, DENSE RANK)
These can be done in a couple of days.
Learning these concepts is NOT hard at all

- what takes time is practice and knowing what command to use when. How do you master that?
- First, create a basic SQL project
- Then, work on an intermediate SQL project (search online) -

Lastly, create something advanced on SQL with many CTEs, subqueries, stored procedures and triggers etc.

This is ALL you need to become a badass in SQL, and trust me when I say this, it is not rocket science. It's just logic.

Remember that practice is the key here. It will be more clear and perfect with the continous practice

Data Analyst Jobs👇

Like this post if it helps 😄❤️

ENJOY LEARNING 👍👍

If you're working with data pipelines, these repositories are very useful: 🚀📊

ibis: A Python API that allows you to write queries once and run them on different data backends, such as DuckDB, BigQuery, and Snowflake. 🐍🔗
https://github.com/ibis-project/ibis

pygwalker: Instantly turns a DataFrame into an interactive UI for visual data exploration. 📈🖥️
https://github.com/Kanaries/pygwalker

katana: A fast and scalable web crawler, often used for security testing and large-scale data collection/search. 🕷️🔒
https://github.com/projectdiscovery/katana

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🔥 SQL Interview Case Studies (Advanced Business Scenarios) 💯

🧠 Case Study 1: Find Repeat Customers
📊 Orders Table
order_id customer_id
1 101
2 102
3 101

❓ Business Question
Find customers who placed more than 1 order.

✅ Solution
SELECT customer_id,
COUNT(*) AS total_orders
FROM orders
GROUP BY customer_id
HAVING COUNT(*) > 1;

🧠 Case Study 2: Highest Paid Employee Per Department
❓ Business Question
Find highest paid employee in every department.

✅ Solution
WITH RankedEmployees AS (
SELECT *,
ROW_NUMBER() OVER(
PARTITION BY department
ORDER BY salary DESC
) rn
FROM employees
)
SELECT *
FROM RankedEmployees
WHERE rn = 1;

🧠 Case Study 3: Find Inactive Customers
❓ Business Question
Customers who haven't ordered in the last 6 months.

✅ Solution
SELECT c.customer_id,
c.name
FROM customers c
LEFT JOIN orders o
ON c.customer_id = o.customer_id
GROUP BY c.customer_id, c.name
HAVING MAX(o.order_date) <
DATE_SUB(CURDATE(), INTERVAL 6 MONTH);

🧠 Case Study 4: Product Generating Highest Revenue
📊 Sales Table
product_id amount

✅ Solution
SELECT product_id,
SUM(amount) AS revenue
FROM sales
GROUP BY product_id
ORDER BY revenue DESC
LIMIT 1;

🧠 Case Study 5: Employee Salary Above Department Average

✅ Solution
WITH DeptAvg AS (
SELECT department,
AVG(salary) avg_salary
FROM employees
GROUP BY department
)

SELECT e.*
FROM employees e
JOIN DeptAvg d
ON e.department = d.department
WHERE e.salary > d.avg_salary;

🧠 Case Study 6: Running Total Sales
❓ Business Question
Calculate cumulative sales.

✅ Solution
SELECT order_date,
amount,
SUM(amount) OVER(
ORDER BY order_date
) AS running_total
FROM sales;

🧠 Case Study 7: Top 3 Products Per Category

✅ Solution
WITH RankedProducts AS (
SELECT *,
ROW_NUMBER() OVER(
PARTITION BY category
ORDER BY sales DESC
) rn
FROM products
)
SELECT *
FROM RankedProducts
WHERE rn <= 3;

🎯 Practice Tasks
1️⃣ Find customer with highest number of orders
2️⃣ Find lowest salary employee per department
3️⃣ Find products never sold
4️⃣ Find departments with average salary > company average
5️⃣ Find month with lowest sales

⚡ Mini Challenge 🔥
Banking Scenario
Tables:
Accounts
account_id customer_name

Transactions
transaction_id account_id amount transaction_date

Question
👉 Find the top 3 customers with highest total transaction amount in the last 1 year.

🔥 Interview Tip
When solving case studies:
1️⃣ Understand business question
2️⃣ Identify tables
3️⃣ Identify JOINs
4️⃣ Identify Aggregations
5️⃣ Decide whether Window Function is needed

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🚀 DSA Topics Every Programmer Should Know 💻🔥

📦 1. Arrays

✔ Traversal

✔ Searching

✔ Sorting

✔ Prefix Sum

✔ Two Pointers

🔤 2. Strings

✔ Character Frequency

✔ Palindromes

✔ Anagrams

✔ String Manipulation

🔗 3. Linked Lists

✔ Singly Linked List

✔ Doubly Linked List

✔ Reverse a Linked List

✔ Fast & Slow Pointers

📚 4. Stacks & Queues

✔ Stack Operations

✔ Queue Operations

✔ Monotonic Stack

✔ Circular Queue

🔑 5. Hashing

✔ HashMap

✔ HashSet

✔ Frequency Counting

✔ Duplicate Detection

🌳 6. Trees

✔ Binary Trees

✔ BST

✔ Tree Traversals

✔ Height & Depth

✔ Lowest Common Ancestor

🌐 7. Graphs

✔ BFS

✔ DFS

✔ Shortest Path

✔ Connected Components

✔ Topological Sorting

🔎 8. Searching & Sorting

✔ Binary Search

✔ Merge Sort

✔ Quick Sort

✔ Heap Sort

🧩 9. Recursion & Backtracking

✔ Recursion Basics

✔ Subsets

✔ Permutations

✔ Combination Problems

✔ N-Queens

⚡ 10. Dynamic Programming

✔ Memoization

✔ Tabulation

✔ 1D & 2D DP

✔ Knapsack Problems

✔ Longest Common Subsequence

⏱️ BONUS: Complexity Analysis

✔ Big-O Notation

✔ Time Complexity

✔ Space Complexity

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🧠 Core Programming Concepts You Should Know 💻🚀

These are the fundamental ideas behind all programming languages.

Understanding them properly builds strong logic and problem-solving skills.

Programming

Programming is the process of writing instructions that a computer can understand and execute. These instructions are written using programming languages like Python, JavaScript, Java, C++, etc.

The goal of programming is to:

• automate tasks

• process data

• build software applications

• control systems and devices

In simple terms, programming tells a computer what to do and how to do it.

Algorithm

An algorithm is a step-by-step method to solve a problem. It focuses on the logic behind solving a problem rather than the specific programming language.

Good algorithms should be:

• Correct → produce the right output

• Efficient → use minimal time and memory

• Clear → easy to understand

For example, searching for a number in a list or sorting data are common algorithm problems.

Flowchart

A flowchart is a diagram that visually represents the logic of a program. Instead of writing code directly, developers sometimes design the program flow using diagrams.

Common flowchart elements include:

• Start / End symbols

• Process blocks

• Decision blocks

• Arrows showing execution flow

Flowcharts help in planning program logic before coding.

Syntax

Syntax refers to the rules that define how code must be written in a programming language. Every programming language has its own syntax. If syntax rules are violated, the program will produce a syntax error and will not run.

Examples of syntax rules include:

• correct use of keywords

• proper structure of statements

• correct punctuation and formatting

Learning syntax is similar to learning the grammar of a language.

Compilation

Compilation is the process of converting human-readable source code into machine code before execution. This is done by a program called a compiler.

Languages that use compilation include:

• C

• C++

• Go

• Rust

Compiled programs usually run faster because the code is already translated into machine instructions.

Interpretation

Interpretation is the process of executing code line by line using an interpreter instead of converting it beforehand. The interpreter reads the code and executes each instruction immediately.

Languages that commonly use interpretation include:

• Python

• JavaScript

• Ruby

Interpreted languages are often easier for beginners because they allow quick testing and debugging.

⭐ Key Idea

Programming concepts like algorithms, syntax, compilation, and interpretation form the foundation of software development. Once these basics are clear, learning any programming language becomes much easier.

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