Day2

day2/rust/src/main.rs

@@ -0,0 +1,48 @@
+use itertools::Itertools;
+
+fn main() {
+    let stdin = std::io::stdin();
+    let mut input = Vec::new();
+
+    for line in stdin.lines() {
+        let line = line.unwrap();
+
+        let levels: Vec<_> = line
+            .split_whitespace()
+            .map(|e| e.parse::<isize>().unwrap())
+            .collect();
+
+        input.push(levels);
+    }
+
+    println!("{}", input.iter().filter(|e| is_safe(e)).count());
+
+    println!(
+        "{}",
+        input
+            .iter()
+            .map(|levels| {
+                levels.iter().combinations(levels.len() - 1).any(|e| {
+                    let combination: Vec<_> = e.into_iter().copied().collect();
+                    is_safe(&combination)
+                })
+            })
+            .filter(|&e| e)
+            .count()
+    );
+}
+
+fn is_safe(levels: &Vec<isize>) -> bool {
+    if levels.len() < 2 {
+        return true;
+    }
+
+    let direction = levels[1] - levels[0];
+
+    return levels
+        .iter()
+        .tuple_windows()
+        .filter(|&(a, b)| (b - a).abs() < 1 || (b - a).abs() > 3 || (b - a) * direction < 0)
+        .count()
+        == 0;
+}