day 10 part 1 first attempt

src/bin/day10.rs

@@ -0,0 +1,146 @@
+#![forbid(elided_lifetimes_in_paths, unsafe_code)]
+
+use aoc23::read;
+use chumsky::prelude::*;
+use std::{
+	collections::{BTreeSet, HashMap, HashSet},
+	fmt::{self, Debug}
+};
+
+macro_rules! cells {
+	($($ident:ident = $char:literal),+) => {
+		#[derive(Clone, Copy, Eq, Hash, PartialEq, PartialOrd, Ord)]
+		enum Cell { $($ident),+ }
+
+		impl Cell {
+			fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
+				choice((
+					$(just($char).map(|_| Self::$ident)),+
+				))
+			}
+		}
+
+		impl Debug for Cell {
+			fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+				match self {
+					$(Self::$ident => write!(f, "{}", $char)),+
+				}
+			}
+		}
+	}
+}
+
+cells! {
+	NorthSouthPipe = '|',
+	EastWestPipe = '-',
+	NorthEastPipe = 'L',
+	NorthWestPipe = 'J',
+	SouthWestPipe = '7',
+	SouthEastPipe = 'F',
+	Ground = '.',
+	Start = 'S'
+}
+
+fn parser() -> impl Parser<char, Vec<Vec<Cell>>, Error = Simple<char>> {
+	Cell::parser()
+		.repeated()
+		.then_ignore(just("\n"))
+		.repeated()
+		.then_ignore(end())
+}
+
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
+struct Node {
+	row: usize,
+	col: usize
+}
+
+#[derive(Default)]
+struct AdjList(HashMap<Node, HashSet<Node>>);
+
+impl AdjList {
+	fn add_edge(&mut self, from: Node, to: Node) {
+		self.0.entry(from).or_default().insert(to);
+		// doesn't work that way due to the way we handle start
+		// self.0.entry(to).or_default().insert(from);
+	}
+
+	fn dij(&self, start: Node) -> HashMap<Node, usize> {
+		let mut dists = HashMap::new();
+		let mut q: BTreeSet<(usize, Node)> = BTreeSet::new();
+
+		dists.insert(start, 0);
+		q.insert((0, start));
+
+		while let Some((dist, node)) = q.pop_first() {
+			for next in self.0.get(&node).into_iter().flatten() {
+				let next_dist = dists.get(next);
+				if next_dist.map(|d| *d > dist + 1).unwrap_or(true) {
+					if let Some(old_dist) = next_dist {
+						q.remove(&(*old_dist, *next));
+					}
+					dists.insert(*next, dist + 1);
+					q.insert((dist + 1, *next));
+				}
+			}
+		}
+
+		dists
+	}
+}
+
+const NORTH: (isize, isize) = (-1, 0);
+const EAST: (isize, isize) = (0, 1);
+const SOUTH: (isize, isize) = (1, 0);
+const WEST: (isize, isize) = (0, -1);
+
+fn main() -> anyhow::Result<()> {
+	let grid = read("inputs/day10.txt", parser())?;
+
+	let mut adj = AdjList::default();
+	let mut start = None;
+	for i in 0 .. grid.len() {
+		for j in 0 .. grid[i].len() {
+			let node = Node { row: i, col: j };
+			let others: &[(isize, isize)] = match grid[i][j] {
+				Cell::NorthSouthPipe => &[NORTH, SOUTH],
+				Cell::EastWestPipe => &[EAST, WEST],
+				Cell::NorthEastPipe => &[NORTH, EAST],
+				Cell::NorthWestPipe => &[NORTH, WEST],
+				Cell::SouthWestPipe => &[SOUTH, WEST],
+				Cell::SouthEastPipe => &[SOUTH, EAST],
+				Cell::Ground => &[],
+				Cell::Start => {
+					assert!(start.is_none());
+					start = Some(node);
+					// we can do this but that means in dijkstra we need to handle
+					// connections going nowhere
+					&[NORTH, EAST, SOUTH, WEST]
+				}
+			};
+			for (row_diff, col_diff) in others {
+				let other = match (
+					i.checked_add_signed(*row_diff),
+					j.checked_add_signed(*col_diff)
+				) {
+					(Some(row), Some(col)) if row < grid.len() && col < grid[i].len() => {
+						Node { row, col }
+					},
+					_ => continue
+				};
+				adj.add_edge(node, other);
+			}
+		}
+	}
+
+	// 6749 is too low
+	println!(
+		"{:?}",
+		adj.dij(start.unwrap())
+			.into_iter()
+			.max_by_key(|(_, dist)| *dist)
+			.unwrap()
+	);
+
+	Ok(())
+}