day 18 2015 in rust

2015/18/rust/Cargo.lock

···
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "rust"
+version = "0.1.0"

2015/18/rust/Cargo.toml

···
+[package]
+name = "rust"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

2015/18/rust/src/main.rs

···
+use std::mem::swap;
+
+#[inline]
+fn get_at(world: &Vec<Vec<bool>>, size: usize, x: isize, y: isize) -> u8 {
+    let isize = size as isize;
+    if x == isize || x == -1 || y == isize || y == -1 {
+        return 0;
+    };
+    if *world
+        .get(y as usize)
+        .expect("invalid position")
+        .get(x as usize)
+        .expect("invalid position")
+    {
+        1
+    } else {
+        0
+    }
+}
+
+#[inline]
+fn get_at_bool(world: &Vec<Vec<bool>>, x: usize, y: usize) -> bool {
+    *world
+        .get(y)
+        .expect("invalid position")
+        .get(x)
+        .expect("invalid position")
+}
+
+fn generations(times: u32, mut world: Vec<Vec<bool>>, size: usize, stuck: bool) -> Vec<Vec<bool>> {
+    let mut new_world = vec![vec![false; size]; size];
+    if stuck {
+        let sizem = size - 1;
+        world[0][0] = true;
+        world[0][sizem] = true;
+        world[sizem][0] = true;
+        world[sizem][sizem] = true;
+    }
+
+    for _ in 0..times {
+        for y in 0..size {
+            for x in 0..size {
+                let xo = x as isize;
+                let yo = y as isize;
+                let xm = xo - 1;
+                let ym = yo - 1;
+                let xp = xo + 1;
+                let yp = yo + 1;
+
+                let was = get_at_bool(&world, x, y);
+                let neighbours = get_at(&world, size, xm, ym)
+                    + get_at(&world, size, xo, ym)
+                    + get_at(&world, size, xp, ym)
+                    + get_at(&world, size, xm, yo)
+                    + get_at(&world, size, xp, yo)
+                    + get_at(&world, size, xm, yp)
+                    + get_at(&world, size, xo, yp)
+                    + get_at(&world, size, xp, yp);
+                new_world[y][x] = neighbours == 3 || (neighbours == 2 && was);
+            }
+        }
+
+        swap(&mut world, &mut new_world);
+
+        // i hate the duplication here :(
+        if stuck {
+            let sizem = size - 1;
+            world[0][0] = true;
+            world[0][sizem] = true;
+            world[sizem][0] = true;
+            world[sizem][sizem] = true;
+        }
+    }
+    world
+}
+
+fn main() {
+    let input = include_str!("../../input.txt").trim();
+    let size = input.split_once("\n").expect("invalid input").0.len();
+    let input: Vec<Vec<bool>> = input
+        .split("\n")
+        .map(|line| line.chars().map(|v| v == '#').collect())
+        .collect();
+
+    let part_1 = generations(100, input.clone(), size, false)
+        .iter()
+        .flatten()
+        .filter(|v| **v)
+        .count();
+    println!("Part 1: {}", part_1);
+
+    let part_2 = generations(100, input.clone(), size, true)
+        .iter()
+        .flatten()
+        .filter(|v| **v)
+        .count();
+    println!("Part 2: {}", part_2);
+}