🧻

Author: Tom-Willemsen

aoc2025_wasm/inputs

@@ -0,0 +1,34 @@
+use anyhow::{Context, Result};
+use ndarray::Array2;
+
+pub fn make_byte_grid(raw_inp: &str) -> Result<Array2<u8>> {
+    let columns = raw_inp
+        .trim()
+        .bytes()
+        .position(|c| c == b'\n')
+        .context("can't get column count")?;
+
+    Array2::from_shape_vec(
+        ((raw_inp.trim().len() + 1) / (columns + 1), columns),
+        raw_inp.bytes().filter(|&x| x != b'\n').collect(),
+    )
+    .context("can't make array")
+}
+
+pub fn make_bool_grid<const TRUE_CHAR: u8>(raw_inp: &str) -> Result<Array2<bool>> {
+    let columns = raw_inp
+        .trim()
+        .bytes()
+        .position(|c| c == b'\n')
+        .context("can't get column count")?;
+
+    Array2::from_shape_vec(
+        ((raw_inp.trim().len() + 1) / (columns + 1), columns),
+        raw_inp
+            .bytes()
+            .filter(|&x| x != b'\n')
+            .map(|b| b == TRUE_CHAR)
+            .collect(),
+    )
+    .context("can't make array")
+}

aoc2025_wasm/src/grid_util.rs

@@ -0,0 +1,81 @@
+use anyhow::Result;
+use ndarray::Array2;
+
+fn neighbour_coords(y: usize, x: usize) -> [(usize, usize); 8] {
+    [
+        (y.wrapping_sub(1), x.wrapping_sub(1)),
+        (y.wrapping_sub(1), x),
+        (y.wrapping_sub(1), x.wrapping_add(1)),
+        (y, x.wrapping_sub(1)),
+        (y, x.wrapping_add(1)),
+        (y.wrapping_add(1), x.wrapping_sub(1)),
+        (y.wrapping_add(1), x),
+        (y.wrapping_add(1), x.wrapping_add(1)),
+    ]
+}
+
+fn neighbours(grid: &Array2<bool>, y: usize, x: usize) -> usize {
+    neighbour_coords(y, x)
+        .into_iter()
+        .filter(|&(y, x)| *grid.get((y, x)).unwrap_or(&false))
+        .count()
+}
+
+fn calculate(mut grid: Array2<bool>) -> (u32, u32) {
+    let mut p1 = 0;
+    let mut p2 = 0;
+    let mut changed_q = Vec::with_capacity(2048);
+
+    for y in 0..grid.dim().0 {
+        for x in 0..grid.dim().1 {
+            if *grid.get((y, x)).expect("indexes are valid") && neighbours(&grid, y, x) < 4 {
+                p1 += 1;
+                changed_q.push((y, x));
+            }
+        }
+    }
+
+    while let Some((y, x)) = changed_q.pop() {
+        {
+            let itm = grid.get_mut((y, x)).expect("indexes are valid");
+            if !*itm {
+                continue;
+            }
+            *itm = false
+        }
+        p2 += 1;
+
+        neighbour_coords(y, x)
+            .into_iter()
+            .filter(|(y, x)| *grid.get((*y, *x)).unwrap_or(&false) && neighbours(&grid, *y, *x) < 4)
+            .for_each(|(y, x)| changed_q.push((y, x)));
+    }
+
+    (p1, p2)
+}
+
+pub fn run_2025_04(inp: &str) -> Result<String> {
+    let grid = crate::grid_util::make_bool_grid::<b'@'>(inp)?;
+    let (p1, p2) = calculate(grid);
+    Ok(format!("{p1}\n{p2}"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EXAMPLE_DATA: &str = include_str!("../inputs/examples/2025_04");
+    const REAL_DATA: &str = include_str!("../inputs/real/2025_04");
+
+    #[test]
+    fn test_example() {
+        let grid = crate::grid_util::make_bool_grid::<b'@'>(EXAMPLE_DATA).unwrap();
+        assert_eq!(calculate(grid), (13, 43));
+    }
+
+    #[test]
+    fn test_real() {
+        let grid = crate::grid_util::make_bool_grid::<b'@'>(REAL_DATA).unwrap();
+        assert_eq!(calculate(grid), (1349, 8277));
+    }
+}

aoc2025_wasm/src/impl_2025_04.rs

@@ -1,6 +1,8 @@
+pub mod grid_util;
 mod impl_2025_01;
 mod impl_2025_02;
 mod impl_2025_03;
+mod impl_2025_04;
 
 pub use wasm_bindgen_rayon::init_thread_pool;
 
@@ -13,6 +15,7 @@ pub fn run_day(day: u32, input: &str) -> String {
         1 => impl_2025_01::run_2025_01(input),
         2 => impl_2025_02::run_2025_02(input),
         3 => impl_2025_03::run_2025_03(input),
+        4 => impl_2025_04::run_2025_04(input),
         _ => Err(anyhow!("No solution for that day yet")),
     };