Coding Exercises

Practical programming challenges — solve tasks within a time limit and see efficient solutions

Tackle problems under time pressure, then compare your approach with the author's solution to learn best practices

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Correct the algorithm for transforming a nested dictionary into a flat one

Correct and optimize an algorithm that transforms a nested dictionary into a flat one, ensuring the correct mapping of key-value pairs....

Guess the Random Number: A Simple Game in C

Guess the Number is a fun exercise aiming to gamify your learning experience of C programming language. With this programming exercise you need implem...

Golang Concurrency Exercise: Debug and Fix Atomic Transaction Bugs

Hands-on Golang concurrency exercise where you'll debug and fix race conditions, deadlocks, and mutex issues in a concurrent bank transfer system. Lea...

The Buggy Basket: A Go Debugging Challenge

Learn Go by debugging a real-world mini project! In this hands-on “Go Grocery Counter” exercise, you’ll fix common Go bugs, master slices, loops, and ...

C Stack Bug Hunt: Fix Two Pop Errors in an RPN Calculator (Pre/Post-Decrement & Underflow)

Fix two bugs in a C postfix expression evaluator — a pop function that decrements before reading returns the wrong stack element, and a missing underf...

C++ Rule of Three: Fix a Double-Free Segfault from a Shallow Copy Constructor

Fix a C++ Buffer class that crashes with a double-free because the compiler-generated copy constructor does a shallow copy of a raw pointer, violating...

Go: Fix a goroutine leak in a timeout wrapper — learn buffered channels and select

Debug a Go timeout wrapper where every timed-out request permanently leaks a goroutine blocked on an unbuffered channel send, causing the goroutine co...

JavaScript exercise: Fix a Promise chain swallowing payment errors — learn re-throwing in .catch()

Debug a JavaScript promise chain in a payment module where a .catch() handler silently swallows gateway errors instead of re-throwing them, testing yo...

CSS: Fix modal rendering behind nav — learn z-index, stacking contexts, and transform side effects

Debug two CSS stacking context bugs that cause a modal dialog to render behind a sticky nav bar despite having a higher z-index — one missing position...

MySQL: Fix Inflated Customer Count in Category Engagement Report

Fix a MySQL Q1 customer engagement report where a bug results in inflating results for categories with repeat purchasers....