From 433efb35ed49be9f2a05e7b8bf2d1cc3987b6bb3 Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Fri, 4 Jul 2025 16:45:46 +0200
Subject: Day 18 2022

---
 2022/18/a.rs      |  7 ++++
 2022/18/b.rs      | 10 ++++++
 2022/18/common.rs | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 112 insertions(+)
 create mode 100644 2022/18/a.rs
 create mode 100644 2022/18/b.rs
 create mode 100644 2022/18/common.rs

diff --git a/2022/18/a.rs b/2022/18/a.rs
new file mode 100644
index 0000000..0713b06
--- /dev/null
+++ b/2022/18/a.rs
@@ -0,0 +1,7 @@
+mod common;
+use common::*;
+
+fn main() {
+    let map = Map::from_stdin();
+    println!("{}", map.total_free_area());
+}
diff --git a/2022/18/b.rs b/2022/18/b.rs
new file mode 100644
index 0000000..a82c213
--- /dev/null
+++ b/2022/18/b.rs
@@ -0,0 +1,10 @@
+mod common;
+use common::*;
+
+fn main() {
+    let mut map = Map::from_stdin();
+    let total_free = map.total_free_area();
+    map.fill_exterior();
+    let interior_free = map.total_free_area() - 6*MAX_LEN*MAX_LEN;
+    println!("{}", total_free - interior_free);
+}
diff --git a/2022/18/common.rs b/2022/18/common.rs
new file mode 100644
index 0000000..ef6c8c8
--- /dev/null
+++ b/2022/18/common.rs
@@ -0,0 +1,95 @@
+pub const MAX_LEN: usize = 20;
+pub const DIR: [(i8, i8, i8); 6] = [
+    (1, 0, 0), (-1, 0, 0), (0, 1, 0), (0, -1, 0), (0, 0, 1), (0, 0, -1)
+];
+
+fn inb(i: i8, j: i8, k: i8) -> bool {
+    i >= 0 && i < MAX_LEN as i8 &&
+    j >= 0 && j < MAX_LEN as i8 &&
+    k >= 0 && k < MAX_LEN as i8
+}
+
+pub struct Map {
+    cell: [[[bool; MAX_LEN]; MAX_LEN]; MAX_LEN]
+}
+
+impl Map {
+    pub fn new() -> Map {
+        Map { cell: [[[false; MAX_LEN]; MAX_LEN]; MAX_LEN] }
+    }
+
+    pub fn from_stdin() -> Map {
+        let mut map = Map::new();
+        let mut line = String::new();
+        while std::io::stdin().read_line(&mut line).unwrap() > 0 {
+            let i = 0;
+            let j = line.find(',').unwrap();
+            let x = line[i..j].parse::<usize>().unwrap();
+            let i = j+1;
+            let j = line[i..].find(',').unwrap() + i;
+            let y = line[i..j].parse::<usize>().unwrap();
+            let i = j+1;
+            let j = line.find('\n').unwrap();
+            let z = line[i..j].parse::<usize>().unwrap();
+            map.set(x, y, z, true);
+            line.clear();
+        }
+        map
+    }
+
+    pub fn get(&self, x: i8, y: i8, z: i8) -> bool {
+        inb(x, y, z) && self.cell[x as usize][y as usize][z as usize]
+    }
+
+    pub fn set(&mut self, x: usize, y: usize, z: usize, b: bool) {
+        self.cell[x][y][z] = b
+    }
+
+    fn free_area(&self, x: usize, y: usize, z: usize) -> usize {
+        let mut r = 0;
+        for d in DIR {
+            let (i, j, k) = (x as i8 + d.0, y as i8 + d.1, z as i8 + d.2);
+            if !self.get(i, j, k) {
+                r += 1
+            }
+        }
+        r
+    }
+
+    pub fn total_free_area(&self) -> usize {
+        let mut r = 0;
+        for i in 0..MAX_LEN {
+            for j in 0..MAX_LEN {
+                for k in 0..MAX_LEN {
+                    if self.get(i as i8, j as i8, k as i8) {
+                        r += self.free_area(i, j, k);
+                    }
+                }
+            }
+        }
+        r
+    }
+
+    #[allow(dead_code)]
+    fn fill_from(&mut self, x: i8, y: i8, z: i8) {
+        if !inb(x, y, z) || self.get(x, y, z) { return; }
+        self.set(x as usize, y as usize, z as usize, true);
+        for d in DIR {
+            self.fill_from(x + d.0, y + d.1, z + d.2);
+        }
+    }
+
+    #[allow(dead_code)]
+    pub fn fill_exterior(&mut self) {
+        for i in 0..MAX_LEN {
+            for j in 0..MAX_LEN {
+                self.fill_from(0 as i8, i as i8, j as i8);
+                self.fill_from((MAX_LEN-1) as i8, i as i8, j as i8);
+                self.fill_from(i as i8, 0 as i8, j as i8);
+                self.fill_from(i as i8, (MAX_LEN-1) as i8, j as i8);
+                self.fill_from(i as i8, j as i8, 0 as i8);
+                self.fill_from(i as i8, j as i8, (MAX_LEN-1) as i8);
+            }
+        }
+    }
+}
-- 
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