Daily Coding Challenges & Projects

Frontend Mini Project Challenge

JavaScript Logical Puzzle:

• Challenge: Write a function to determine whether a number is a "happy number."

A number is happy if replacing it with the sum of squares of its digits repeatedly eventually results in 1.

Example: 19 → 1² + 9² = 82 → 8² + 2² = 68 → ... → 1

Debugging Challenge:

function isEven(num) {
  return num % 2 = 0;
}
console.log(isEven(4)); // What's wrong?

• Task: Find and fix the bug.
• Try it online: JSFiddle / CodePen

Backend Challenge

C/C++/C#

• Problem:
• Language: C
• Task: Write a C program to reverse a singly linked list without using recursion

Database Query Challenge

Problems on SQL - HR Database :

1. Find all employees who were hired in the last 90 days.
• Hint: Use SYSDATE and hire_date.
2. Find employees who don’t have any manager assigned.
• Hint: Look for manager_id IS NULL.

Structure of HR database :

Validate Submit Reset

Data Structures & Algorithms Challenge

• Easy:
• Problem: Find the first non-repeating character in a string.
• Hint: Use a hash map to track frequency.
• Medium:
• Problem: Implement a queue using two stacks.
• Hint: Stack push/pop logic mimics FIFO.
• Hard:
• Problem: Find the longest increasing subsequence in an array.
• Hint: Use dynamic programming with O(n²) or optimize with binary search.

Bug of the Day

Language: C

Go Bug:

#include 
int main() {
    int a = 5;
    if (a = 10) {
        printf("Equal\n");
    }
    return 0;
}

Challenge: Identify and fix the bug in this C code.

📋 Daily Micro-Project

Frontend Focus

• Task: Build a CSS-only toggle button with "ON/OFF" states

No JavaScript allowed. Use checkbox hack or focus+label styles

Trivia: 5 Fun Facts

1. Linus Torvalds created Linux in 1991.
2. Java was initially called "Oak."
3. The first computer bug was a literal moth.
4. Python is named after Monty Python, not the snake.
5. Tim Berners-Lee invented the World Wide Web in 1989.

Tool of the Day

Tool: JSFiddle

What It Does:Online playground for testing JavaScript, CSS, HTML live.

Bonus Resource: MDN Web Docs - JavaScript

Interview Question of the Day

Daily Interview Questions

Frontend (JavaScript) : (4 Questions)
1. What is the difference between null and undefined in JS?
2. How does event delegation work?
3. What is hoisting in JavaScript?
4. Explain the purpose of use strict.

Backend :
1. What is the difference between a thread and a process?
2. Explain memory allocation in C.
3. What are pointers and how are they used?
4. What are system-level calls in C?

Database (3 Questions)
1. What is the difference between JOIN and UNION?
2. What is a primary key?
3. Explain the difference between clustered and non-clustered indexes.

Others ( OS & DevOps ) : (2 Questions)
1. What is an operating system kernel?
2. How is virtualization different from containerization?

Daily Quiz Challenge

Frontend ( 3 Questions ) :

1. What will console.log(typeof null) print?
• null
• object
• undefined
• function
2. Which of the following is not a primitive in JS?
• string
• number
• object
• boolean
3. What is the output of console.log(1 + '1')?
• 2
• 11
• NaN
• Error

Backend ( 3 Questions ) :

1. What is the file extension for C header files?
• .ch
• .c
• .h
• .cpp
2. Which of the following is a correct way to define a pointer in C?
• int ptr;
• int *ptr;
• ptr int*;
• pointer int;
3. Which keyword is used to allocate dynamic memory in C?
• new
• malloc
• alloc
• heap

Database & Other Quiz ( 2 Questions ) :

1. What does COUNT(*) do in SQL?
• Counts only non-null values
• Counts all rows
• Counts nulls only
• Returns NULL if no row
2. What is the output of len("hello") in Python?
• 4
• 5
• Error
• None

Weekly Cross-Domain Activities ( April 11 to 17, 2025 )

API of the Day:

Integrate NASA’s Astronomy Picture of the Day (APOD) API.

• Challenge: Integrate NASA’s APOD API to fetch and display the Astronomy Picture of the Day.
• API URL: api.nasa.gov/
• Steps to Implement:
1. Get an API Key – Sign up on NASA’s website to obtain a free API key.
2. Fetch Data – Use fetch() (JavaScript) or requests (Python) to retrieve the latest image.
3. Display the Image & Description – Show the image along with its title and explanation.
4. Bonus Features:
• Add a date picker to fetch past images.
• Implement dark mode for better UX.
• Allow users to download images or share them on social media.

• Tech Stack Options:
• Frontend: JavaScript (React/Vue) for fetching and displaying data.
• Backend (Optional): Node.js/Python backend to cache results and reduce API calls.

Linux/DevOps Tip:

Monitor server performance using htop and vmstat.

Why? Monitoring system performance helps in identifying CPU/memory bottlenecks.

Using htop (Interactive Process Viewer)

• Installation:

sudo apt install htop   # Debian/Ubuntu
sudo yum install htop   # RHEL/CentOS

• Command:

htop

• Features:
• Displays CPU, RAM, Swap usage in real-time.
• Shows running processes, sorted by CPU/memory.
• Allows killing processes directly.
• Use F5 for tree view, F9 to kill a process.

Using vmstat (System Performance Metrics)

• Command:

vmstat 5 10

• 5: Update every 5 seconds.
• 10: Run 10 updates and stop.
• Metrics Explained:
• r (run queue) – Number of processes waiting to run.
• b (blocked) – Processes blocked on I/O.
• swpd – Swap memory usage.
• us, sy, id – User, system, and idle CPU time.
• si, so – Swap-in, swap-out activity.

Pro Tip:

• Combine htop and vmstat with iostat for deeper disk performance analysis.
• Use tmux to keep monitoring running even after disconnecting from SSH.

Real-World Project of the Week ( April 11 to 17, 2025 )

Project of the Week: Build a Personal Task Manager App (Frontend + Backend + Database)

Goal: Develop a simple but functional task manager where users can add, update, delete, and mark tasks as completed.

Tech Stack Options:

• Frontend: React, Vue.js, or Svelte for a dynamic UI.
• Backend: Node.js with Express, Django (Python), or Spring Boot (Java) for API handling.
• Database: PostgreSQL, MongoDB, or Firebase for data storage.

Features to Implement:

• User Authentication: Allow users to sign up/login using email & password (or OAuth).
• Task Management: Users can create, edit, and delete tasks.
• Task Status Updates: Mark tasks as completed/incomplete.
• Due Dates & Reminders: Allow users to set due dates and get notifications.
• Categories & Filters: Organize tasks by priority or category.
• Dark Mode & Responsive Design: Ensure mobile compatibility.

Bonus Features:

• Add a calendar view for better visualization.
• Implement speech-to-text for quick task creation.
• Allow users to drag & drop tasks to change priority.

APIs to Use:

• Google Calendar API (for reminders).
• Web Push Notifications (for task reminders).

Collaborative Project: Open-Source Expense Tracker using React & Node.js

Goal: Build a fully functional open-source expense tracker that logs and categorizes daily expenses.

Tech Stack:

• Frontend: React + TailwindCSS for a sleek UI.
• Backend: Node.js with Express + JWT for authentication.
• Database: MongoDB (NoSQL) for flexibility or PostgreSQL (SQL) for structured data.

Core Features:

• User Authentication: Secure login & signup with JWT.
• Expense Logging: Users can add daily expenses with categories.
• Charts & Analytics: Visualize spending with graphs (Recharts/D3.js).
• Export Data: Users can download expense reports in CSV format.
• Multi-Currency Support: Convert expenses into different currencies.

Bonus Features:

• Connect with Plaid API to fetch transactions from banks.
• Add AI-based spending insights (e.g., detect high spending trends).
• Implement PWA (Progressive Web App) for offline tracking.

Open Source Contribution:

• Host on GitHub: Encourage contributions (features, bug fixes).
• Use GitHub Projects & Issues: Manage development tasks efficiently.
• Create a Wiki/Docs: Guide contributors on setting up the project.

Case Study: How Netflix Optimizes Streaming Using Microservices

Overview:

Netflix, the world’s largest streaming platform, handles millions of concurrent users while delivering high-quality video streaming. It achieves this using a microservices architecture running on AWS.

Key Technologies Used:

• Microservices: Each function (authentication, recommendations, video encoding) runs as an independent service.
• AWS (Amazon Web Services): Netflix uses EC2, S3, Lambda, and DynamoDB for scalable cloud operations.
• CDN (Content Delivery Network): Netflix caches videos in Open Connect Appliances (OCA) placed worldwide to reduce latency.
• Dynamic Adaptive Streaming: Uses MPEG-DASH & HLS to adjust video quality in real-time based on internet speed.
• Chaos Engineering: Netflix runs "Chaos Monkey" to simulate failures and improve system resilience.

Lessons for Developers:

• Design for Scalability: Use microservices instead of a monolithic approach.
• Optimize Performance: Utilize caching & CDNs to reduce response time.
• Fault Tolerance: Simulate failures in production to test system robustness.
• Data-Driven Personalization: Netflix's recommendation engine is powered by big data & AI models analyzing user behavior.