[2025] Finish day 12

and thats all for aoc 2025

Author: connorslade

README.md

@@ -16,6 +16,7 @@ Thank you to [Eric Wastl](http://was.tl) for running this incredible yearly even
 - [Day 09: Movie Theater](aoc_2025/src/day_09.rs)
 - [Day 10: Factory](aoc_2025/src/day_10.rs)
 - [Day 11: Reactor](aoc_2025/src/day_11.rs)
+- [Day 12: Christmas Tree Farm](aoc_2025/src/day_12.rs)
 <!-- MARKER -->
 
 ## [2024](https://adventofcode.com/2024) [![aoc_2024](https://github.com/connorslade/advent-of-code/actions/workflows/aoc_2024.yml/badge.svg)](https://github.com/connorslade/advent-of-code/actions/workflows/aoc_2024.yml)

aoc_2025/src/day_12.rs

@@ -0,0 +1,106 @@
+use common::{Answer, solution};
+use nd_vec::{Vec2, vector};
+
+solution!("Christmas Tree Farm", 12);
+
+#[derive(Debug)]
+struct Tree {
+    size: Vec2<u32>,
+    counts: Vec<u32>,
+}
+
+fn part_a(input: &str) -> Answer {
+    let (presents, trees) = parse(input);
+
+    (trees.iter())
+        .filter(|tree| {
+            (presents.iter().zip(tree.counts.iter()))
+                .map(|(present, count)| *present as u32 * *count)
+                .sum::<u32>()
+                <= tree.size.x() * tree.size.y()
+        })
+        .count()
+        .into()
+}
+
+fn part_b(_input: &str) -> Answer {
+    Answer::Unimplemented
+}
+
+fn parse(input: &str) -> (Vec<usize>, Vec<Tree>) {
+    let (presents_raw, trees_raw) = input.rsplit_once("\n\n").unwrap();
+
+    let mut presents = Vec::new();
+    for present in presents_raw.split("\n\n") {
+        let raw = present[present.find('\n').unwrap()..].trim();
+        presents.push(raw.chars().filter(|x| *x == '#').count());
+    }
+
+    let mut trees = Vec::new();
+    for tree in trees_raw.lines() {
+        let (size, counts) = tree.split_once(": ").unwrap();
+
+        let (width, height) = size.split_once('x').unwrap();
+        let size = vector!(width.parse().unwrap(), height.parse().unwrap());
+
+        let counts = counts
+            .split_whitespace()
+            .map(|x| x.parse::<u32>().unwrap())
+            .collect::<Vec<_>>();
+
+        trees.push(Tree { size, counts });
+    }
+
+    (presents, trees)
+}
+
+#[cfg(test)]
+mod test {
+    use indoc::indoc;
+
+    const CASE: &str = indoc! {"
+        0:
+        ###
+        ##.
+        ##.
+
+        1:
+        ###
+        ##.
+        .##
+
+        2:
+        .##
+        ###
+        ##.
+
+        3:
+        ##.
+        ###
+        ##.
+
+        4:
+        ###
+        #..
+        ###
+
+        5:
+        ###
+        .#.
+        ###
+
+        4x4: 0 0 0 0 2 0
+        12x5: 1 0 1 0 2 2
+        12x5: 1 0 1 0 5 2
+    "};
+
+    #[test]
+    fn part_a() {
+        assert_eq!(super::part_a(CASE), 2.into());
+    }
+
+    #[test]
+    fn part_b() {
+        assert_eq!(super::part_b(CASE), ().into());
+    }
+}

aoc_2025/src/lib.rs

@@ -11,6 +11,7 @@ mod day_08;
 mod day_09;
 mod day_10;
 mod day_11;
+mod day_12;
 // [import_marker]
 
 pub const SOLUTIONS: &[Solution] = &[
@@ -25,5 +26,6 @@ pub const SOLUTIONS: &[Solution] = &[
     day_09::SOLUTION,
     day_10::SOLUTION,
     day_11::SOLUTION,
+    day_12::SOLUTION,
     // [list_marker]
 ];