Daily Coding Challenges & Projects

Frontend Mini Project Challenge

Theme : JavaScript Logical Puzzles + JavaScript Debugging

Small Challenge 1 — JavaScript Logical Puzzle :

Challenge

Write a function that returns the first non-repeating character in a string.

But here’s the twist → You cannot use any built-in string methods like indexOf or lastIndexOf.

Example :

Input: "aabbcddee"
Output: "c"

Small Challenge 2 — Debugging Challenge

Buggy Code :

function sum(arr) {
  return arr.reduce((a, b) => {
    a + b;
  });
}
console.log(sum([1, 2, 3]));

Task :

Find the bug and fix why this returns undefined instead of 6.

Interactive Playground Suggestions :

• JSFiddle
• CodePen
• StackBlitz

Backend Challenge

Focus : C, C++, C#

C Challenge :

Write a function to rotate an array by k positions without using extra array memory.

C++ Challenge :

Create a function that detects whether a linked list contains a cycle, using only O(1) extra memory (Floyd’s cycle algorithm).

C# Challenge :

Write a C# method that reads a 3GB log file line-by-line and prints only lines containing a specific keyword — without loading the whole file into memory.

Database Query Challenge

Problems on SQL - HR Database :

1. Find employees whose salary is above the department average.
2. List employees who have not changed departments in the last 5 years, ordered by hire date.

Data Structures & Algorithms Challenge

• Easy:
• Problem : Return true if an array is sorted in non-decreasing order.
• Hint :One pass → Compare each element with the previous one.
• Medium:
• Problem : Given an array, find the maximum sum of any contiguous subarray (Kadane’s Algorithm).
• Hint :Keep track of current sum + global max.
• Hard:
• Problem : Implement a Trie (prefix tree) with insert, search, and startsWith operations.
• Hint :Use a hashmap/dictionary for children at each node.

Bug of the Day

Focus : C, C++, C#

Buggy Code ( C ) :

int *p;
*p = 10;
printf("%d", *p);

Why does this crash? Fix it.

Buggy Code ( C++ ) :

string s = "hello";
s[5] = '!';
cout << s;

Identify buffer issue.

Buggy Code ( C# ) :

int x = null;
Console.WriteLine(x);

Find the semantic error.

📋 Daily Micro-Project

Focus : Frontend

Task :

Build a "Dynamic Character Counter" component

Requirements :

• Works like Twitter:
• Show remaining characters
• Turns red when limit exceeded
• Must support: JS / React / Vue

Bonus : Add a progress circle animation in CSS

Trivia: 5 Fun Facts

1. The first version of C was created in 1972 at Bell Labs.
2. The original Java mascot was named Duke.
3. C++ was initially called “C with Classes”.
4. React was created inside Facebook’s Ads team in 2013.
5. The world’s first computer programmer was Ada Lovelace (1843).

Tool & Resource of the Day

Tool : Valgrind

A powerful tool for detecting memory leaks in C/C++.

Resource Roundup :

• Free guide: "Advanced Memory Management in C" ( PDFs available on many university sites ).

Interview Question of the Day

Daily Interview Questions

Frontend :
1. Explain event bubbling in JavaScript.
2. What is function hoisting?
3. How do arrow functions differ from regular functions in JS?
4. Explain the this keyword in JavaScript with an example.

Backend :
1. How does a stack differ from a heap in C/C++?
2. What is a segmentation fault?
3. Explain CLR in C#.
4. What is the purpose of garbage collection in C#?

Database :
1. What is a foreign key?
2. Explain normalization (1NF, 2NF, 3NF).
3. What is a composite key?

Others :
1. What is a kernel?
2. What is multithreading?

Daily Quiz Challenge

Frontend :

1. What is the output of console.log([] == 0)?
2. Which JS method converts JSON string to object?
3. What does "use strict" do?

Backend :

1. What does malloc() return when memory allocation fails?
2. What is the difference between struct and class in C++?
3. What is the base class of all C# types?

Database :

1. Which SQL clause is applied after GROUP BY?

Other :

2. Which protocol does SSH run on — TCP or UDP?

Mixed Quiz :

3. What is the time complexity of accessing an element in:
• JS array
• SQL indexed column
• C++ vector

Weekly Cross-Domain Activities ( November 22 to November 27, 2025 )

API of the Day:

Integrate the OpenWeatherMap API and build a small weather widget showing temperature, city, and weather icon.

Linux / DevOps Tip :

Use top, htop, and vmstat to monitor CPU, memory, and process usage live on Linux servers.

Real-World Project of the Week ( November 22 to November 27, 2025 )

Project of the Week:

Build a “Personal Finance Tracker” — Track expenses, visualize data with charts, and store in a backend DB.

Collaborative Project :

Contribute to an open-source Habit Tracker App on GitHub (Frontend: React, Backend: Node.js).

Case Study :

Study how Spotify’s recommendation system works — replicate a mini version using a dataset and cosine similarity.