day18

src/bin/day18_1.rs

@@ -0,0 +1,8 @@
+use std::fs;
+
+use aoc2022::day18::process_part_1;
+
+fn main() {
+    let file = fs::read_to_string("./inputs/day18.txt").unwrap();
+    println!("{}", process_part_1(&file));
+}

src/bin/day18_2.rs

@@ -0,0 +1,8 @@
+use std::fs;
+
+use aoc2022::day18::process_part_2;
+
+fn main() {
+    let file = fs::read_to_string("./inputs/day18.txt").unwrap();
+    println!("{}", process_part_2(&file));
+}

src/day18.rs

@@ -0,0 +1,102 @@
+use std::collections::HashSet;
+
+use nom::character::complete;
+use nom::character::complete::newline;
+use nom::combinator::opt;
+use nom::multi::fold_many1;
+use nom::sequence::{preceded, terminated, tuple};
+use nom::IResult;
+
+pub fn sides((x, y, z): (i32, i32, i32)) -> [(i32, i32, i32); 6] {
+    [
+        (x + 1, y, z),
+        (x - 1, y, z),
+        (x, y + 1, z),
+        (x, y - 1, z),
+        (x, y, z + 1),
+        (x, y, z - 1),
+    ]
+}
+
+pub fn process_part_1(input: &str) -> usize {
+    let drops = parse_input(input).unwrap().1;
+
+    drops
+        .iter()
+        .flat_map(|&v| sides(v))
+        .filter(|v| !drops.contains(v))
+        .count()
+}
+
+pub fn process_part_2(input: &str) -> usize {
+    let drops = parse_input(input).unwrap().1;
+    // Flood fill Bounding box so we don't go too far out of sanity, its a dumb bounding box though
+    let max = drops.iter().flat_map(|&(x, y, z)| [x, y, z]).max().unwrap() + 1;
+    let mut seen = HashSet::new();
+    let mut stack = vec![(0, 0, 0)];
+
+    while let Some(pos) = stack.pop() {
+        for (x, y, z) in sides(pos) {
+            if !drops.contains(&(x, y, z))
+                && !seen.contains(&(x, y, z))
+                && [x, y, z].iter().all(|&i| -1 <= i && i <= max)
+            {
+                seen.insert((x, y, z));
+                stack.push((x, y, z));
+            }
+        }
+    }
+
+    drops
+        .iter()
+        .flat_map(|&v| sides(v))
+        .filter(|v| seen.contains(v))
+        .count()
+}
+
+fn parse_input(input: &str) -> IResult<&str, HashSet<(i32, i32, i32)>> {
+    fold_many1(parse_line, HashSet::new, |mut set, v| {
+        set.insert(v);
+        set
+    })(input)
+}
+
+fn parse_line(input: &str) -> IResult<&str, (i32, i32, i32)> {
+    terminated(
+        tuple((
+            complete::i32,
+            preceded(complete::char(','), complete::i32),
+            preceded(complete::char(','), complete::i32),
+        )),
+        opt(newline),
+    )(input)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = "2,2,2
+1,2,2
+3,2,2
+2,1,2
+2,3,2
+2,2,1
+2,2,3
+2,2,4
+2,2,6
+1,2,5
+3,2,5
+2,1,5
+2,3,5";
+
+    #[test]
+    fn day1() {
+        assert_eq!(process_part_1(INPUT), 64);
+    }
+
+    #[test]
+    fn day2() {
+        assert_eq!(process_part_2(INPUT), 58);
+    }
+}

src/lib.rs

@@ -18,3 +18,4 @@ pub mod day14;
 pub mod day15;
 pub mod day16;
 pub mod day17;
+pub mod day18;