1 files changed, 38 insertions, 0 deletions
diff --git a/2024/2/p1.rs b/2024/2/p1.rs
new file mode 100644
index 0000000..4e4df46
--- /dev/null
+++ b/2024/2/p1.rs
@@ -0,0 +1,38 @@
+const INPUT_FILE: &str = "input";
+
+#[derive(PartialEq, Clone, Copy)]
+enum Direction {
+    Up,
+    Down,
+    Unknown,
+}
+use Direction::*;
+
+fn is_safe(levels: &[u32]) -> bool {
+    let mut direction = Unknown;
+    for i in 0..levels.len()-1 {
+        let [x, y] = levels[i..=i+1] else { panic!("unreachable") };
+        let (diff, d) = if x > y { (x-y, Down) } else { (y-x, Up) };
+        if direction == Unknown {
+            direction = d;
+        }
+        if diff == 0 || diff > 3 || direction != d {
+            return false;
+        }
+    }
+    return true;
+}
+
+fn main() {
+    let input = std::fs::read_to_string(INPUT_FILE).unwrap();
+
+    let mut total = 0;
+    for report in input.lines() {
+        let levels: Vec<u32> =
+            report.split_whitespace().map(|l| l.parse().unwrap()).collect();
+        if is_safe(&levels) {
+            total += 1;
+        }
+    }
+    println!("Levels! {:?}", total);
+}