Daily Coding Challenges & Projects

Frontend Mini Project Challenge

Theme : JavaScript Logical Puzzles, Debugging

Challenge :

Write a JavaScript function that takes an array of integers and returns the first number that repeats twice in sequence.

Example :

findRepeat([1, 2, 2, 3, 4, 4, 5]) // Output: 2

Backend Challenge

Focus : C, C++, C#

C Programming Challenge :

Write a C program to implement a stack using linked list with the following operations:

• Push
• Pop
• Peek
• Check if empty

Bonus : Optimize memory usage by freeing unused nodes immediately.

C++ Challenge :

Implement a template-based priority queue (min-heap) in C++ without using STL.

• Insert an element
• Delete minimum
• Peek minimum

C# Challenge :

Write a C# console app that simulates a basic banking system with classes:

• Account (id, name, balance)
• Methods : Deposit, Withdraw, Transfer

Database Query Challenge

Problems on SQL - HR Database :

1. Write a query to find employees who are managers but do not have any subordinates in the HR database.
2. Write a query to list employees whose salary is above the department’s average salary.

Data Structures & Algorithms Challenge

• Easy:
• Problem : Find the first non-repeating character in a string.
• Hint :Use HashMap/Set
• Medium:
• Problem : Given a string, find the length of the longest substring without repeating characters.
• Hint :Sliding Window + HashMap
• Hard:
• Problem : Find the maximum subarray sum after at most one element deletion.
• Hint :Divide & Conquer, Segment Tree/Fenwick Tree

Bug of the Day

Focus : C, C++, C#

Buggy Code ( C ) :

#include 
int main() {
    int arr[5] = {1,2,3,4,5};
    for(int i=0; i<=5; i++) {
        printf("%d\n", arr[i]);
    }
    return 0;
}

Challenge: Identify and fix the bug(s).

📋 Daily Micro-Project

Focus : Backend

Task :

Build a JavaScript-powered digital clock that updates every second and displays time in HH:MM:SS format.

Trivia: 5 Fun Facts

1. The first computer bug was a real moth found in a Harvard Mark II computer in 1947.
2. The "C" language was developed in 1972 by Dennis Ritchie at Bell Labs.
3. The first website ever created is still online: info.cern.ch.
4. Python was named after the comedy series Monty Python’s Flying Circus, not the snake.
5. The first version of JavaScript was written in just 10 days by Brendan Eich in 1995.

Tool & Resource of the Day

Tool : Postman

• Simplifies API testing.
• Allows automation with collections.
• Great for debugging backend services.

Resource Roundup :

• Free Postman Learning Center: learning.postman.com
• Beginner-friendly API testing guide: Postman Beginner Tutorial

Interview Question of the Day

Daily Interview Questions

Frontend :
1. What is the difference between null and undefined in JavaScript?
2. Explain how event delegation works in JavaScript.
3. How does React’s Virtual DOM improve performance?
4. In Vue.js, what’s the difference between computed properties and watchers?

Backend :
1. What is the difference between a thread and a process?
2. Explain synchronous vs. asynchronous programming in Node.js.
3. How does garbage collection work in C#?
4. Explain REST vs. GraphQL with an example.

Database :
1. What’s the difference between INNER JOIN and LEFT JOIN?
2. How do clustered indexes differ from non-clustered indexes?
3. Explain normalization and why it’s important.

Others :
1. What are system calls in OS? Give an example.
2. What is containerization, and how does Docker simplify deployment?

Daily Quiz Challenge

Frontend :

1. What is the output?

console.log([] + []);

• []
• ""
• undefined
• null
2. Which CSS property is used to create transitions?
• transform
• transition
• animation
• keyframes
3. In Vue.js, which directive is used for two-way binding?
• v-model
• v-bind
• v-if
• v-for

Backend :

1. Which keyword is used in C to dynamically allocate memory?
• malloc
• new
• alloc
• calloc
2. In C++, which principle does "inheritance" represent?
• Abstraction
• Encapsulation
• Reusability
• Polymorphism
3. In C#, what does async keyword represent?
• Asynchronous method execution
• Memory optimization
• Data encapsulation
• Thread locking

Database :

1. Which SQL clause is used to filter grouped rows?
• WHERE
• GROUP BY
• HAVING
• ORDER BY

Other :

2. Who is known as the father of the C programming language?
• Ken Thompson
• Dennis Ritchie
• Brian Kernighan
• James Gosling

Mixed Quiz :

3. Which of the following is NOT true about REST APIs?
• Stateless communication
• Uses HTTP methods like GET, POST, PUT, DELETE
• Requires a specific programming language
• Can return data in JSON or XML

Weekly Cross-Domain Activities ( September 12 to September 18, 2025 )

API of the Day:

Integrate the NASA Astronomy Picture of the Day API and display today’s image.

Linux / DevOps Tip : Use df -h to check disk usage and du -sh for folder sizes.

Real-World Project of the Week ( September 12 to September 18, 2025 )

Project of the Week:

Build a habit tracker app ( Frontend: React/Vue + Backend: Node.js/Scala + DB: PostgreSQL).

Collaborative Project :

Join the open-source project FreeCodeCamp

Case Study :

Study how Netflix handles recommendations using collaborative filtering.