aoc23/src/bin/day1.rs

#![forbid(elided_lifetimes_in_paths, unsafe_code)]

use aoc23::read;
use chumsky::prelude::*;
use std::{io::{BufReader, BufRead}, fs::File};
use chumsky::chain::Chain;

struct Line {
	first_digit: u128,
	last_digit: u128
}

// thanks rust
fn array<T, const N: usize>(array: &'static [T; N]) -> &'static [T] {
	array
}

impl Line {
	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
		choice((
			// digit combinations (only the relevant ones)
			just("oneight").map(|_| array(&[1, 8])),
			just("twoone").map(|_| array(&[2, 1])),
			just("eightwo").map(|_| array(&[8, 2])),

			// single digits
			just("one").or(just("1")).map(|_| array(&[1])),
			just("two").or(just("2")).map(|_| array(&[2])),
			just("three").or(just("3")).map(|_| array(&[3])),
			just("four").or(just("4")).map(|_| array(&[4])),
			just("five").or(just("5")).map(|_| array(&[5])),
			just("six").or(just("6")).map(|_| array(&[6])),
			just("seven").or(just("7")).map(|_| array(&[7])),
			just("eight").or(just("8")).map(|_| array(&[8])),
			just("nine").or(just("9")).map(|_| array(&[9])),

			// garbage
			none_of(['1', '2', '3', '4', '5', '6', '7', '8', '9', '\n'])
				.map(|_| array(&[]))
		))
		.repeated()
		.then_ignore(just('\n'))
		.map(|digits: Vec<&'static [u128]>| {
			let mut digits = digits.into_iter().flat_map(|array| array.iter().copied());
			let first_digit = digits.next().expect("No digit in line");
			let last_digit = digits.last().unwrap_or(first_digit);
			Line {
				first_digit,
				last_digit
			}
		})
	}
}

fn parser() -> impl Parser<char, Vec<Line>, Error = Simple<char>> {
	Line::parser().repeated().then_ignore(end())
}

fn main() -> anyhow::Result<()> {
	let lines = read("inputs/day1.txt", parser())?;

	let sum: u128 = lines
		.iter()
		.map(|line| line.first_digit * 10 + line.last_digit)
		// .map(|number| { eprintln!("{number}"); number })
		.sum();
	println!("{sum}");

	let mut sum: u128 = 0;
	for line in BufReader::new(File::open("inputs/day1.txt")?).lines() {
		let line = line?;
		let line = line.trim();
		if line.is_empty() {
			continue;
		}

		let mut digits = Vec::new();
		for i in 0 .. line.len() {
			let s = &line[i..];

			macro_rules! check_digit {
				($digit:literal, $string:literal) => {
					if s.starts_with(stringify!($digit)) || line[i..].starts_with($string) {
						digits.push($digit);
					}
				}
			}

			check_digit!(1, "one");
			check_digit!(2, "two");
			check_digit!(3, "three");
			check_digit!(4, "four");
			check_digit!(5, "five");
			check_digit!(6, "six");
			check_digit!(7, "seven");
			check_digit!(8, "eight");
			check_digit!(9, "nine");
		}
		sum += digits.first().unwrap() * 10 + digits.last().unwrap();
	}
	println!("{sum}");

	Ok(())
}