day 17

Author: erning

README.md

@@ -66,4 +66,8 @@ Part Two: 48568
 --- Day 16: Ticket Translation ---
 Part One: 25916
 Part Two: 2564529489989
+
+--- Day 17: Conway Cubes ---
+Part One: 237
+Part Two: 2448
 ```

inputs/17-example.txt

@@ -0,0 +1,3 @@
+.#.
+..#
+###

inputs/17-input.txt

@@ -0,0 +1,8 @@
+####...#
+......##
+####..##
+##......
+..##.##.
+#.##...#
+....##.#
+.##.#.#.

src/day17.rs

@@ -0,0 +1,147 @@
+use std::collections::HashSet;
+
+fn parse_input(input: &str) -> Vec<Vec<char>> {
+    input.lines().map(|s| s.chars().collect()).collect()
+}
+
+pub fn part_one(input: &str) -> usize {
+    let grid = parse_input(input);
+    let h = grid.len();
+    let w = grid[0].len();
+    let mut cubes: HashSet<(i32, i32, i32)> = grid
+        .iter()
+        .enumerate()
+        .flat_map(|(y, row)| {
+            row.iter().enumerate().filter_map(move |(x, &c)| {
+                if c == '#' {
+                    Some((x as i32, y as i32, 0))
+                } else {
+                    None
+                }
+            })
+        })
+        .collect();
+
+    fn process_cube(
+        pos: (i32, i32, i32),
+        cube: &HashSet<(i32, i32, i32)>,
+        new_cubes: &mut HashSet<(i32, i32, i32)>,
+    ) {
+        let neighbors = {
+            let mut count = 0;
+            for x in -1..=1 {
+                for y in -1..=1 {
+                    for z in -1..=1 {
+                        if x == 0 && y == 0 && z == 0 {
+                            continue;
+                        }
+                        if cube.contains(&(pos.0 + x, pos.1 + y, pos.2 + z)) {
+                            count += 1;
+                        }
+                    }
+                }
+            }
+            count
+        };
+        if neighbors == 3 || (cube.contains(&pos) && neighbors == 2) {
+            new_cubes.insert(pos);
+        }
+    }
+
+    let mut new_cubes = HashSet::new();
+    for i in 1..=6 {
+        for x in -i..w as i32 + i {
+            for y in -i..h as i32 + i {
+                for z in -i..=i {
+                    process_cube((x, y, z), &cubes, &mut new_cubes);
+                }
+            }
+        }
+        cubes = new_cubes;
+        new_cubes = HashSet::new();
+    }
+
+    cubes.len()
+}
+
+pub fn part_two(input: &str) -> usize {
+    let grid = parse_input(input);
+    let h = grid.len();
+    let w = grid[0].len();
+    let mut cubes: HashSet<(i32, i32, i32, i32)> = grid
+        .iter()
+        .enumerate()
+        .flat_map(|(y, row)| {
+            row.iter().enumerate().filter_map(move |(x, &c)| {
+                if c == '#' {
+                    Some((x as i32, y as i32, 0, 0))
+                } else {
+                    None
+                }
+            })
+        })
+        .collect();
+
+    fn process_cube(
+        pos: (i32, i32, i32, i32),
+        cube: &HashSet<(i32, i32, i32, i32)>,
+        new_cubes: &mut HashSet<(i32, i32, i32, i32)>,
+    ) {
+        let neighbors = {
+            let mut count = 0;
+            for x in -1..=1 {
+                for y in -1..=1 {
+                    for z in -1..=1 {
+                        for w in -1..=1 {
+                            if x == 0 && y == 0 && z == 0 && w == 0 {
+                                continue;
+                            }
+                            if cube.contains(&(
+                                pos.0 + x,
+                                pos.1 + y,
+                                pos.2 + z,
+                                pos.3 + w,
+                            )) {
+                                count += 1;
+                            }
+                        }
+                    }
+                }
+            }
+            count
+        };
+        if neighbors == 3 || (cube.contains(&pos) && neighbors == 2) {
+            new_cubes.insert(pos);
+        }
+    }
+
+    let mut new_cubes = HashSet::new();
+    for i in 1..=6 {
+        for x in -i..w as i32 + i {
+            for y in -i..h as i32 + i {
+                for z in -i..=i {
+                    for w in -i..=i {
+                        process_cube((x, y, z, w), &cubes, &mut new_cubes);
+                    }
+                }
+            }
+        }
+        cubes = new_cubes;
+        new_cubes = HashSet::new();
+    }
+
+    cubes.len()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::read_example;
+
+    #[test]
+    fn example() {
+        let input = read_example(17);
+        assert_eq!(part_one(&input), 112);
+        assert_eq!(part_two(&input), 848);
+    }
+}

src/lib.rs

@@ -16,6 +16,7 @@ pub mod day13;
 pub mod day14;
 pub mod day15;
 pub mod day16;
+pub mod day17;
 
 pub fn read_as_string(day: u8, filename: &str) -> String {
     let filename = format!("inputs/{:02}-{}.txt", day, filename);

src/main.rs

@@ -32,6 +32,7 @@ fn main() {
         puzzle!(day14, "Docking Data"),
         puzzle!(day15, "Rambunctious Recitation"),
         puzzle!(day16, "Ticket Translation"),
+        puzzle!(day17, "Conway Cubes"),
     ];
 
     let filename = match env::args().find(|a| a == "--example") {