How should I structure a Rust project for solving small coding challenges?

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I have been doing Project Euler problems (mathematical coding challenges) for a while.

In the past I have been coding them up in Python (where it is simple to have dozens of scripts in the same project). However, I am now redoing some of the challenges as I learn Rust. I have found it pretty awkward to work on these projects as I can't simply write a bunch of Rust programs in the same directory but it also seems very excessive to create a whole new Rust project for each program.

Can anyone recommend a good intermediary? Ideally I'm looking for something similar to the aforementioned Python project with a bunch of separate scripts.

project-structure rust
1 Answers

I would recommend this project structure for working through coding challenges:

/src/bin/problem-101.rs
/src/bin/problem-143.rs
/src/lib.rs
/Cargo.toml

Essentially just create a project like cargo new --lib challenges, create a bin/ folder in src/, create separate source files for each problem in there, and off you go!

//! /src/bin/problem-101.rs
fn main() {
    println!("solution #101")
}

//! /src/bin/problem-143.rs
fn main() {
    println!("solution #143")
}

//! /src/lib.rs
pub fn add(left: usize, right: usize) -> usize {
    left + right
}

# Cargo.toml
[package]
name = "challenges"
version = "0.1.0"
edition = "2021"

[dependencies]
# dependencies are shared between all problems

This structure is easy to use and extend with small "scripts" because Rust source files in the /src/bin folder are automatically detected as binaries and do not need to be listed separately in Cargo.toml. You can run them directly:

> cargo run --bin problem-101
   Compiling challenges v0.1.0 (...\challenges)
    Finished dev [unoptimized + debuginfo] target(s) in 0.26s
     Running `target\debug\problem-101.exe`
solution #101
> cargo run --bin problem-143
   Compiling challenges v0.1.0 (...\challenges)
    Finished dev [unoptimized + debuginfo] target(s) in 0.32s
     Running `target\debug\problem-143.exe`
solution #143

Using a library as the root of the project allows you to share functions and logic between your problems very easily. Just import from the library like so:

use challenges::add;

The only step up from here would be to use workspaces which would give you fine-grained dependencies for each problem, but that requires separate folders, separate Cargo.tomls, separate src/ directories so you probably don't want that for simple coding challenges.

kmdreko0
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