Code Challenges

My solutions to Coding Challenges by John Crickett — built from scratch in Kotlin with GraalVM native images.

Each challenge is a standalone Gradle subproject under challenges/ with its own tests, native binary, and write-up.

Challenges

#	Challenge	Problem	Description
1	wc	Challenge	Word, line, byte & character counting
2	json-parser	Challenge	Recursive-descent JSON lexer & parser
3	compression-tool	Challenge	Huffman coding compression
4	cut-tool	Challenge	Field extraction (delimiters & byte ranges)
5	load-balancer	Challenge	HTTP reverse proxy with health checks
6	sort-tool	Challenge	Four sorting algorithms (merge, quick, heap, radix)
7	calculator	Challenge	Shunting-yard expression evaluator
8	redis-server	Challenge	RESP protocol server with virtual threads
9	grep	Challenge	Line-by-line regex pattern matching
10	uniq	Challenge	Streaming adjacent-duplicate filtering
11	web-server	Challenge	HTTP/1.1 server from raw sockets
12	url-shortener	Challenge	SHA-256 hashing & REST API from raw sockets
13	diff	Challenge	Longest common subsequence diff
14	shell	Challenge	REPL with pipes, builtins & job control
15	cat	Challenge	File concatenation & line numbering
16	irc-client	Challenge	Real-time IRC chat over raw TCP

Tech Stack

• Kotlin on JDK 21
• GraalVM Native Image (Oracle GraalVM 24) for AOT-compiled binaries
• JUnit 5 for testing
• Gradle multi-project build with shared conventions

Getting Started

# Build & test a specific challenge
./gradlew :challenges:wc:test

# Build native binary
./gradlew :challenges:wc:nativeCompile

# Install to /usr/local/bin (requires sudo)
./gradlew :challenges:wc:install

Project Structure

challenges/
  wc/                  # Each challenge is a standalone subproject
    src/main/kotlin/   # Implementation
    src/test/kotlin/   # Tests
    ARTICLE.md         # Write-up explaining the approach
    build.gradle.kts   # Applies shared challenge-conventions plugin
buildSrc/              # Shared Gradle convention plugin

Each challenge includes an ARTICLE.md with a detailed write-up covering the design, algorithms, and usage.