2024 day 25

Author: ictrobot

crates/year2024/examples/day25_example0.txt

@@ -0,0 +1,39 @@
+#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####

crates/year2024/src/day25.rs

@@ -0,0 +1,75 @@
+use utils::prelude::*;
+
+/// Finding matching keys and locks.
+#[derive(Clone, Debug)]
+pub struct Day25 {
+    locks: Vec<u32>,
+    keys: Vec<u32>,
+}
+
+impl Day25 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        let mut locks = Vec::new();
+        let mut keys = Vec::new();
+
+        for item in parser::one_of((b'.'.map(|_| false), b'#'.map(|_| true)))
+            .repeat_n::<5, _>(parser::noop())
+            .repeat_n::<7, _>(parser::eol())
+            .with_suffix(parser::eol().then(parser::eol()))
+            .parse_iterator(input)
+        {
+            let grid = item?;
+
+            let top = grid[0][0];
+            let bottom = grid[6][0];
+            if top == bottom
+                || grid[0][1..].iter().any(|&x| x != top)
+                || grid[6][1..].iter().any(|&x| x != bottom)
+            {
+                return Err(InputError::new(input, 0, "expected lock or key"));
+            }
+
+            let mut mask = 0u32;
+            for c in 0..5 {
+                let mut h = 0;
+                for row in grid[1..].iter() {
+                    if row[c] != top {
+                        break;
+                    }
+                    h += 1;
+                }
+                mask |= ((1 << h) - 1) << (c * 5);
+            }
+
+            if top {
+                locks.push(mask);
+            } else {
+                keys.push(mask);
+            }
+        }
+
+        Ok(Self { locks, keys })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> u32 {
+        let mut total = 0;
+        for &lock in &self.locks {
+            for &key in &self.keys {
+                if lock & key == lock {
+                    total += 1;
+                }
+            }
+        }
+        total
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> &'static str {
+        "🎄"
+    }
+}
+
+examples!(Day25 -> (u32, &'static str) [
+    {file: "day25_example0.txt", part1: 3},
+]);

crates/year2024/src/lib.rs

@@ -26,4 +26,5 @@ utils::year!(2024 => year2024, ${
     22 => day22::Day22,
     23 => day23::Day23,
     24 => day24::Day24,
+    25 => day25::Day25,
 });