day 3 part 2

src/bin/day3.rs

@@ -60,27 +60,51 @@ fn main() -> anyhow::Result<()> {
 	let grid = read("inputs/day3.txt", parser())?;
 
 	let mut sum = 0;
+	let mut possible_gears: HashMap<(usize, usize), Vec<usize>> = HashMap::new();
 	for (i, line) in grid.iter().enumerate() {
-		'entities: for (col, ent) in &line.entities {
+		for (col, ent) in &line.entities {
 			let Entity::Number { num, len } = ent else {
 				continue;
 			};
 
-			// see if adjacent
+			let mut adjacent = false;
 			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) {
+					if let Some(Entity::Symbol(symbol)) = row.entities.get(&search_col) {
+						adjacent = true;
+						if *symbol == '*' {
+							possible_gears
+								.entry((search_row, search_col))
+								.or_default()
+								.push(*num);
+						}
+					}
+				}
+			}
+
+			if adjacent {
 				sum += num;
-						continue 'entities;
-					}
-				}
 			}
 		}
 	}
 	println!("{sum}");
+	println!(
+		"{}",
+		possible_gears
+			.values()
+			.filter_map(|nums| {
+				let mut nums = nums.iter();
+				let ratio = nums.next()? * nums.next()?;
+				let None = nums.next() else {
+					return None;
+				};
+				Some(ratio)
+			})
+			.sum::<usize>()
+	);
 
 	Ok(())
 }