day 14 part 1

src/bin/day14.rs

@@ -0,0 +1,80 @@
+#![forbid(elided_lifetimes_in_paths, unsafe_code)]
+
+use aatree::AATreeSet;
+use aoc23::read;
+use chumsky::prelude::*;
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum Cell {
+	Void,
+	RollingStone,
+	PermanentStone
+}
+
+impl Cell {
+	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
+		choice((
+			just('.').map(|_| Self::Void),
+			just('O').map(|_| Self::RollingStone),
+			just('#').map(|_| Self::PermanentStone)
+		))
+	}
+}
+
+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 grid = read("inputs/day14.txt", parser())?;
+
+	let mut rolling_stones: AATreeSet<(usize, usize)> = grid
+		.iter()
+		.enumerate()
+		.flat_map(|(i, row)| {
+			row.iter()
+				.enumerate()
+				.filter(|(_, stone)| **stone == Cell::RollingStone)
+				.map(move |(j, _)| (i, j))
+		})
+		.collect();
+
+	// we skip the first row, no stones can be rolled north
+	let mut last_row = 0;
+	let mut last_col = grid[0].len();
+
+	while let Some((row, col)) = rolling_stones
+		.first_at_or_after(&(last_row, last_col + 1))
+		.copied()
+	{
+		let mut new_row = row;
+		while new_row > 0
+			&& !rolling_stones.contains(&(new_row - 1, col))
+			&& grid[new_row - 1][col] != Cell::PermanentStone
+		{
+			new_row -= 1;
+		}
+		if new_row != row {
+			rolling_stones.remove(&(row, col));
+			rolling_stones.insert((new_row, col));
+		}
+		last_row = row;
+		last_col = col;
+	}
+
+	let mut weight = 0;
+	for col in 0 .. grid[0].len() {
+		for row in 0 .. grid.len() {
+			if rolling_stones.contains(&(row, col)) {
+				weight += grid.len() - row;
+			}
+		}
+	}
+	println!("{weight}");
+
+	Ok(())
+}