solution: day 25

data/examples/25.txt

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

src/bin/25.rs

@@ -0,0 +1,57 @@
+pub fn part_one(input: &str) -> Option<usize> {
+    let mut keys = Vec::new();
+    let mut locks = Vec::new();
+
+    for key_or_lock in input.split("\n\n") {
+        let lock = key_or_lock
+            .lines()
+            .next()
+            .unwrap()
+            .chars()
+            .all(|x| x == '#');
+
+        let mut columns = [0; 5];
+        for (idx, c) in key_or_lock.lines().flat_map(|x| x.chars().enumerate()) {
+            if c == '#' {
+                columns[idx] += 1;
+            }
+        }
+
+        // remove top or bottom row from count
+        for c in columns.iter_mut() {
+            *c -= 1;
+        }
+
+        if lock {
+            locks.push(columns);
+        } else {
+            keys.push(columns);
+        }
+    }
+
+    let mut count = 0;
+    for k in keys.iter() {
+        for l in locks.iter() {
+            if k.iter().zip(l.iter()).all(|(k, l)| k + l <= 5) {
+                count += 1;
+            }
+        }
+    }
+
+    count.into()
+}
+
+pub fn part_two(_input: &str) -> Option<String> {
+    "Happy christmas!".to_string().into()
+}
+
+aoc::solution!(25);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(part_one(&aoc::template::read_file("examples", 25)), Some(3));
+    }
+}