Hangman-Rust

Hangman in Rust

Module: COMP10068 — Secure Programming | UWS
Language: Rust | Assignment: Build a fully functional Hangman game from a bare Hello World template

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Overview

A complete Hangman game built in Rust, demonstrating Rust's memory-safety model, ownership semantics, and standard library patterns. The starting point was a single main() function printing Hello world — everything else was built from scratch.

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How It Works

Round starts → load fruits.txt → deduplicate → pick random fruit
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Display hidden word (underscores for letters, spaces/apostrophes visible)
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Player guesses letter or full word
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     ├─ Correct letter → reveal all matching positions
     ├─ Wrong letter   → deduct attempt, show remaining
     ├─ Full word match → win immediately
     ├─ Full word wrong → deduct attempt, hint: "X letters match"
     └─ Repeated guess  → penalise (no free re-guesses)
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Win (no underscores remain) or Lose (0 attempts left → reveal word)
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Play again? (Enter/y → new round, n → exit)

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Design Decisions

Duplicate Handling

fruits.txt contains repeated entries — Banana appears 10 times, Blood orange appears twice. Rather than editing the file (which was marked uneditable per the brief), entries are collected into a HashSet which drops duplicates automatically, then converted to a Vec for random selection:

let unique: HashSet<&str> = contents.lines()
    .map(|l| l.trim())
    .filter(|l| !l.is_empty())
    .collect();

Unicode-Safe Display

The fruit list includes multi-word names (Blood orange) and names with apostrophes (Buddha's hand). Spaces and apostrophes are revealed from the first turn — hiding them would make the puzzle unsolvable. Letters only are replaced with underscores:

Blood orange  →  _____ ______
Buddha's hand →  _______'_ ____

Guess Validation

• All input converted to lowercase immediately — case-insensitive guessing
• Input length determines guess type: single character = letter guess, multiple = word attempt
• Repeated letter guesses are penalised — prevents free enumeration
• Wrong word guesses provide a hint: number of letters that appear in the secret word

Game Structure

Split into two functions for clean state management:

• main() — handles the play-again loop between rounds
• play_game() — contains all logic for a single round with its own clean state

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Why Rust for Secure Programming

Rust enforces memory safety at compile time — the classes of vulnerabilities fixed in Assignment 1 (buffer over-reads, memory leaks, use-after-free) cannot exist in safe Rust:

C++ Vulnerability (Assignment 1)	Rust Equivalent
Buffer over-read (STR50-CPP)	Bounds-checked by default — panic on out-of-bounds access
Memory leak (MEM51-CPP)	Ownership system — memory freed automatically when owner goes out of scope
Use-after-free	Borrow checker — compiler rejects use of moved or dropped values
Null pointer dereference	No null pointers — Option<T> forces explicit handling of absent values

This is not just a game — it is a demonstration of what a memory-safe systems language looks like in practice.

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Running the Game

# Ensure fruits.txt is in the project root
cargo run

Requirements: Rust toolchain (rustup), rand crate (declared in Cargo.toml)

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Files

File	Description
B00249469_ErmandMani_Hangman_solution.pdf	Assignment report — design decisions, implementation approach, references

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Disclaimer

Assignment completed individually as part of COMP10068 assessed coursework at UWS.