1 files changed, 52 insertions, 0 deletions
diff --git a/src/bin/day2.rs b/src/bin/day2.rs
new file mode 100644
index 0000000..e34b8b0
--- /dev/null
+++ b/src/bin/day2.rs
@@ -0,0 +1,52 @@
+static DAY: u8 = 2;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", safe_reports(&input));
+    println!("{DAY}b: {}", 0);
+}
+
+fn is_report_safe(report: &[i32]) -> bool {
+    let increasing = report[1] - report[0] > 0;
+    for number in report.iter().as_slice().windows(2) {
+        let diff = number[1] - number[0];
+        if diff.abs() < 1 || diff.abs() > 3 {
+            return false;
+        }
+        if (diff > 0) != increasing {
+            return false;
+        }
+    }
+    true
+}
+
+fn safe_reports(input: &[String]) -> usize {
+    let mut reports = Vec::new();
+    for line in input {
+        let numbers = line.split(" ")
+                          .map(|x| x.parse::<i32>().unwrap())
+                          .collect::<Vec<_>>();
+        reports.push(numbers);
+    }
+    reports.iter()
+           .filter(|x| is_report_safe(x))
+           .count()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "7 6 4 2 1",
+            "1 2 7 8 9",
+            "9 7 6 2 1",
+            "1 3 2 4 5",
+            "8 6 4 4 1",
+            "1 3 6 7 9",
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+        assert_eq!(safe_reports(&input), 2);
+    }
+}