2022 day 18

2022/src/day18/part1.rs

@@ -0,0 +1,35 @@
+use std::collections::HashSet;
+use std::fs::File;
+use std::io::{BufRead,BufReader};
+use std::str::FromStr;
+
+
+pub fn main() {
+	let input_file = File::open("input").expect("File open");
+	let reader = BufReader::new(input_file);
+	let mut grid = HashSet::new();
+	for line in reader.lines().map(|l| l.unwrap()) {
+		let parts: Vec<&str> = line.split(",").collect();
+		if parts.len() != 3 { panic!(); }
+		let mut coords = [0;3];
+		for (i, istr) in line.split(",").enumerate() {
+			coords[i] = u8::from_str(istr).unwrap();
+		}
+		grid.insert(coords);
+	}
+
+	let mut open_faces = 0;
+	for coords in grid.iter() {
+		for (i,c) in coords.iter().enumerate() {
+			if !grid.contains(&with_coord(coords, i, c + 1)) { open_faces += 1; }
+			if *c == 0 || !grid.contains(&with_coord(coords, i, c - 1)) { open_faces += 1; }
+		}
+	}
+	println!("{open_faces}");
+}
+
+fn with_coord(existing: &[u8;3], i: usize, new: u8) -> [u8;3] {
+	let mut new_coord = existing.clone();
+	new_coord[i] = new;
+	new_coord
+}

2022/src/day18/part2.rs

@@ -0,0 +1,57 @@
+use std::collections::HashSet;
+use std::fs::File;
+use std::io::{BufRead,BufReader};
+use std::str::FromStr;
+
+
+pub fn main() {
+	let input_file = File::open("input").expect("File open");
+	let reader = BufReader::new(input_file);
+	let mut filled = HashSet::new();
+	let mut min_coord = 0;
+	let mut max_coord = 0;
+	for line in reader.lines().map(|l| l.unwrap()) {
+		let parts: Vec<&str> = line.split(",").collect();
+		if parts.len() != 3 { panic!(); }
+		let mut coords = [0;3];
+		for (i, istr) in line.split(",").enumerate() {
+			coords[i] = i8::from_str(istr).unwrap();
+			if coords[i] < min_coord { min_coord = coords[i]; }
+			if coords[i] > max_coord { max_coord = coords[i]; }
+		}
+		filled.insert(coords);
+	}
+
+	let origin = [max_coord + 1;3];
+	let mut queue = vec![origin];
+	let mut exposed = HashSet::from([origin]);
+	let mut open_faces = 0;
+	while let Some(coords) = queue.pop() {
+		for (i,c) in coords.iter().enumerate() {
+			if *c <= max_coord {
+				let pos = with_coord(&coords, i, c + 1);
+				if filled.contains(&pos) {
+					open_faces += 1;
+				} else if exposed.insert(pos) {
+					queue.push(pos);
+				}
+			}
+
+			if *c >= min_coord  {
+				let neg = with_coord(&coords, i, c - 1);
+				if filled.contains(&neg) {
+					open_faces += 1;
+				} else if exposed.insert(neg) {
+					queue.push(neg);
+				}
+			}
+		}
+	}
+	println!("{open_faces}");
+}
+
+fn with_coord(existing: &[i8;3], i: usize, new: i8) -> [i8;3] {
+	let mut new_coord = existing.clone();
+	new_coord[i] = new;
+	new_coord
+}