day 11 part 1

src/bin/day11.rs

@@ -0,0 +1,83 @@
+#![forbid(elided_lifetimes_in_paths, unsafe_code)]
+
+use aoc23::read;
+use chumsky::prelude::*;
+use std::collections::HashSet;
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum Cell {
+	Void,
+	Galaxy
+}
+
+impl Cell {
+	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
+		choice((
+			just('.').map(|_| Self::Void),
+			just('#').map(|_| Self::Galaxy)
+		))
+	}
+}
+
+fn parser() -> impl Parser<char, Vec<Vec<Cell>>, Error = Simple<char>> {
+	Cell::parser()
+		.repeated()
+		.then_ignore(just("\n"))
+		.repeated()
+		.then_ignore(end())
+}
+
+fn main() -> anyhow::Result<()> {
+	let universe = read("inputs/day11.txt", parser())?;
+
+	let empty_rows: HashSet<usize> = universe
+		.iter()
+		.enumerate()
+		.filter(|(_, row)| row.iter().all(|cell| *cell == Cell::Void))
+		.map(|(i, _)| i)
+		.collect();
+	let empty_cols: HashSet<usize> = universe
+		.first()
+		.unwrap()
+		.iter()
+		.enumerate()
+		.map(|(i, _)| i)
+		.filter(|i| universe.iter().all(|row| row[*i] == Cell::Void))
+		.collect();
+
+	let galaxies: Vec<(usize, usize)> = universe
+		.iter()
+		.enumerate()
+		.flat_map(|(i, row)| row.iter().enumerate().map(move |(j, cell)| (i, j, *cell)))
+		.filter(|(_, _, cell)| *cell == Cell::Galaxy)
+		.map(|(i, j, _)| (i, j))
+		.collect();
+
+	let mut sum = 0_u64;
+	for (i, g) in galaxies.iter().enumerate() {
+		for (_j, h) in galaxies.iter().enumerate().skip(i + 1) {
+			let mut x = [g.0, h.0];
+			x.sort_unstable();
+			let mut dist = (x[0] .. x[1])
+				.map(|row| match empty_rows.contains(&row) {
+					true => 2,
+					false => 1
+				})
+				.sum::<u64>();
+
+			let mut y = [g.1, h.1];
+			y.sort_unstable();
+			dist += (y[0] .. y[1])
+				.map(|col| match empty_cols.contains(&col) {
+					true => 2,
+					false => 1
+				})
+				.sum::<u64>();
+			// eprintln!(" - Between galaxy {} and galaxy {}: {dist}", i + 1, _j + 1);
+			sum += dist;
+		}
+	}
+	println!("{sum}");
+
+	Ok(())
+}