day 3 part 1

src/bin/day3.rs

@@ -0,0 +1,86 @@
+#![forbid(elided_lifetimes_in_paths, unsafe_code)]
+
+use aoc23::read;
+use chumsky::{prelude::*, text::int};
+use std::collections::HashMap;
+
+enum Entity {
+	Void,
+	Symbol(char),
+	Number { num: usize, len: usize }
+}
+
+impl Entity {
+	fn len(&self) -> usize {
+		match self {
+			Self::Void | Self::Symbol(_) => 1,
+			Self::Number { len, .. } => *len
+		}
+	}
+
+	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
+		choice((
+			just('.').map(|_| Self::Void),
+			int(10).map(|num: String| Self::Number {
+				num: num.parse().unwrap(),
+				len: num.len()
+			}),
+			none_of(['\n']).map(Self::Symbol)
+		))
+	}
+}
+
+struct Line {
+	entities: HashMap<usize, Entity>
+}
+
+impl Line {
+	fn parser() -> impl Parser<char, Self, Error = Simple<char>> {
+		Entity::parser().repeated().map(|line| {
+			let mut col = 0;
+			let mut entities = HashMap::new();
+			for ent in line {
+				let len = ent.len();
+				entities.insert(col, ent);
+				col += len;
+			}
+			Line { entities }
+		})
+	}
+}
+
+fn parser() -> impl Parser<char, Vec<Line>, Error = Simple<char>> {
+	Line::parser()
+		.then_ignore(just("\n"))
+		.repeated()
+		.then_ignore(end())
+}
+
+fn main() -> anyhow::Result<()> {
+	let grid = read("inputs/day3.txt", parser())?;
+
+	let mut sum = 0;
+	for (i, line) in grid.iter().enumerate() {
+		'entities: for (col, ent) in &line.entities {
+			let Entity::Number { num, len } = ent else {
+				continue;
+			};
+
+			// see if adjacent
+			for search_row in i.saturating_sub(1) ..= i + 1 {
+				let Some(row) = grid.get(search_row) else {
+					continue;
+				};
+				for search_col in col.saturating_sub(1) ..= col + len {
+					if let Some(Entity::Symbol(_)) = row.entities.get(&search_col) {
+						sum += num;
+						continue 'entities;
+					}
+				}
+			}
+		}
+	}
+	println!("{sum}");
+
+	Ok(())
+}