inputs/day6.txt

@@ -1,2 +0,0 @@
-Time:        42     68     69     85
-Distance:   284   1005   1122   1341

src/bin/day6.rs

@@ -1,77 +0,0 @@
-#![forbid(elided_lifetimes_in_paths, unsafe_code)]
-
-use aoc23::read;
-use chumsky::{prelude::*, text::int};
-
-struct Game {
-	time: i64,
-	distance: i64
-}
-
-fn parser() -> impl Parser<char, Vec<Game>, Error = Simple<char>> {
-	let int_list = just(" ")
-		.repeated()
-		.ignore_then(int(10).separated_by(just(" ").repeated().at_least(1)));
-	just("Time:")
-		.ignore_then(int_list)
-		.then_ignore(just("\nDistance:"))
-		.then(int_list)
-		.map(|(times, dists): (Vec<String>, Vec<String>)| {
-			times
-				.into_iter()
-				.zip(dists)
-				.map(|(time, distance)| Game {
-					time: time.parse().unwrap(),
-					distance: distance.parse().unwrap()
-				})
-				.collect()
-		})
-		.then_ignore(just("\n"))
-		.then_ignore(end())
-}
-
-fn ways2win(t: i64, d: i64) -> i64 {
-	// we want the minimum a s.t. (t-a)*a > d,
-	// and the maximum a s.t.     (t-a)*a < d
-	// that means we have a quadratic function -a² + ta - d and we want to find
-	// its intersections with the axis
-
-	let discriminant = t * t - 4 * d;
-	if discriminant < 0 {
-		return 0;
-	}
-	let sqrt = (discriminant as f64).sqrt();
-	let min = ((t as f64 - sqrt) / 2.0).ceil() as i64;
-	let max = ((t as f64 + sqrt) / 2.0).floor() as i64;
-	eprintln!(
-		"t={t}, d={d}, min={min} ({}), max={max} ({})",
-		(t - min) * min,
-		(t - max) * max
-	);
-	assert!(max >= min);
-
-	max - min + 1
-}
-
-fn main() -> anyhow::Result<()> {
-	let games = read("inputs/day6.txt", parser())?;
-
-	println!(
-		"{}",
-		games
-			.iter()
-			.map(|game| ways2win(game.time, game.distance))
-			.product::<i64>()
-	);
-
-	let mut t = 0;
-	let mut d = 0;
-	for game in &games {
-		t = t * 10i64.pow((game.time as f64).log10().floor() as u32 + 1) + game.time;
-		d = d * 10i64.pow((game.distance as f64).log10().floor() as u32 + 1)
-			+ game.distance;
-	}
-	println!("{}", ways2win(t, d));
-
-	Ok(())
-}