Solution for day 24 (part 2)

day24/Cargo.toml

@@ -7,3 +7,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+ndarray = "0.14.0"

day24/src/game.rs

@@ -0,0 +1,121 @@
+use ndarray::Array2;
+
+use crate::locations::{CellLocation, MINICUBE_DIFF_ARRAY};
+
+struct CellInfo {
+    is_alive: bool, // alive = black, dead = white
+    alive_minicube_count: usize,
+}
+
+impl Default for CellInfo {
+    fn default() -> CellInfo {
+        CellInfo {
+            is_alive: false,
+            alive_minicube_count: 0,
+        }
+    }
+}
+
+impl CellInfo {
+    pub fn set_alive(&mut self) {
+        self.is_alive = true;
+    }
+
+    pub fn add_alive_minicube(&mut self) {
+        self.alive_minicube_count += 1;
+    }
+
+    pub fn set_dead(&mut self) {
+        self.is_alive = false;
+    }
+
+    pub fn add_dead_minicube(&mut self) {
+        self.alive_minicube_count -= 1;
+    }
+}
+
+pub struct Game {
+    board: Array2<CellInfo>,
+    corner: CellLocation,
+}
+
+impl Game {
+    fn make_alive(&mut self, cell_location: CellLocation) {
+        self.board[cell_location].set_alive();
+        for &diff in &MINICUBE_DIFF_ARRAY {
+            self.board[cell_location + diff].add_alive_minicube();
+        }
+    }
+
+    fn make_dead(&mut self, cell_location: CellLocation) {
+        self.board[cell_location].set_dead();
+        for &diff in &MINICUBE_DIFF_ARRAY {
+            self.board[cell_location + diff].add_dead_minicube();
+        }
+    }
+
+    pub fn next_step(&mut self) -> usize {
+        let mut new_alive: Vec<_> = vec![];
+        let mut new_dead: Vec<_> = vec![];
+        for x in 0..self.corner.x {
+            for y in 0..self.corner.y {
+                let location = CellLocation { x, y };
+                match &self.board[location] {
+                    CellInfo { is_alive: true, alive_minicube_count } if *alive_minicube_count == 0 || *alive_minicube_count > 2 => {
+                        new_dead.push(location);
+                    },
+                    CellInfo { is_alive: false, alive_minicube_count: 2 } => {
+                        new_alive.push(location);
+                    },
+                    _ => {}
+                }
+            }
+        }
+
+        let changes_count = new_alive.len() + new_dead.len();
+        for location in new_alive {
+            self.make_alive(location);
+        }
+        for location in new_dead {
+            self.make_dead(location);
+        }
+
+        changes_count
+    }
+
+    pub fn from_input(input_data: &[(i16, i16)], max_number_of_steps: usize) -> Self {
+        let min_x = input_data.iter().map(|(x, _y)| *x).min().unwrap();
+        let max_x = input_data.iter().map(|(x, _y)| *x).max().unwrap();
+        let min_y = input_data.iter().map(|(_x, y)| *y).min().unwrap();
+        let max_y = input_data.iter().map(|(_x, y)| *y).max().unwrap();
+        let input_size_x = max_x - min_x;
+        let input_size_y = max_y - min_y;
+        let size_x = (input_size_x as usize) + max_number_of_steps * 2;
+        let size_y = (input_size_y as usize) + max_number_of_steps * 2;
+        let offset_x = (max_number_of_steps as i16) - min_x;
+        let offset_y = (max_number_of_steps as i16) - min_y;
+        let corner = CellLocation {
+            x: size_x,
+            y: size_y,
+        };
+        let board = Array2::default((corner.x, corner.y));
+        let mut game = Game {
+            board,
+            corner,
+        };
+
+        for (input_x, input_y) in input_data {
+            game.make_alive(CellLocation {
+                x: (input_x + offset_x) as usize,
+                y: (input_y + offset_y) as usize,
+            });
+        }
+
+        return game;
+    }
+
+    pub fn get_alive_count(&self) -> usize {
+        (&self.board).iter().filter(|&cell| cell.is_alive).count()
+    }
+}
+

day24/src/locations.rs

@@ -0,0 +1,49 @@
+use std::ops::{Add, Index, IndexMut};
+
+use ndarray::Array2;
+
+#[derive(Copy, Clone)]
+pub struct CellDiff {
+    x: i8,
+    y: i8,
+}
+
+pub const MINICUBE_DIFF_ARRAY: [CellDiff; 6] = [
+    CellDiff { x: -1, y:  0 },
+    CellDiff { x:  0, y:  1 },
+    CellDiff { x:  1, y:  1 },
+    CellDiff { x:  1, y:  0 },
+    CellDiff { x:  0, y: -1 },
+    CellDiff { x: -1, y: -1 },
+];
+
+#[derive(Copy, Clone)]
+pub struct CellLocation {
+    pub x: usize,
+    pub y: usize,
+}
+
+impl Add<CellDiff> for CellLocation {
+    type Output = Self;
+
+    fn add(self, other: CellDiff) -> Self {
+        CellLocation {
+            x: (self.x as isize + other.x as isize) as usize,
+            y: (self.y as isize + other.y as isize) as usize,
+        }
+    }
+}
+
+impl<T> Index<CellLocation> for Array2<T> {
+    type Output = T;
+    fn index<'a>(&'a self, cell_location: CellLocation) -> &'a T {
+        &self[[cell_location.x, cell_location.y]]
+    }
+}
+
+impl<T> IndexMut<CellLocation> for Array2<T> {
+    fn index_mut<'a>(&'a mut self, cell_location: CellLocation) -> &'a mut T {
+        &mut self[[cell_location.x, cell_location.y]]
+    }
+}
+

day24/src/main.rs

@@ -1,35 +1,47 @@
 use std::collections::HashSet;
 use std::io::{self, BufRead};
 
+mod game;
+mod locations;
+
+use crate::game::Game;
+
+const MAX_NUMBER_OF_STEPS: usize = 100;
+
 fn main() {
     let stdin = io::stdin();
-    let mut changed_tiles = HashSet::new();
+    let mut alive_tiles = HashSet::new();
     for line_result in stdin.lock().lines() {
-        let processed_line = line_result.unwrap().replace("nw", "7").replace("ne", "9").replace("sw", "1").replace("se", "3");
-        let mut x = 0;
-        let mut y = 0;
+        let processed_line = line_result.unwrap().replace("nw", "n").replace("se", "s");
+        let mut x = 0i16;
+        let mut y = 0i16;
         for ch in processed_line.chars() {
             x += match ch {
-                'e' => 2,
-                'w' => -2,
-                '9' | '3' => 1,
-                '7' | '1' => -1,
+                'e' => 1,
+                'w' => -1,
                 _ => 0,
             };
             y += match ch {
-                '9' | '7' => 1,
-                '3' | '1' => -1,
+                'n' => 1,
+                's' => -1,
                 _ => 0,
             };
         }
 
         let tile = (x, y);
-        if changed_tiles.contains(&tile) {
-            changed_tiles.remove(&tile);
+        if alive_tiles.contains(&tile) {
+            alive_tiles.remove(&tile);
         } else {
-            changed_tiles.insert(tile);
+            alive_tiles.insert(tile);
         }
     }
 
-    println!("{}", changed_tiles.len());
+    let mut game = Game::from_input(&alive_tiles.iter().cloned().collect::<Vec<_>>(), MAX_NUMBER_OF_STEPS);
+
+    println!("{}", game.get_alive_count());
+
+    for i in 1..=MAX_NUMBER_OF_STEPS {
+        game.next_step();
+        println!("Day {}: {}", i, game.get_alive_count());
+    }
 }