Day 2

data/examples/02.txt

@@ -0,0 +1,6 @@
+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

src/bin/02.rs

@@ -0,0 +1,70 @@
+advent_of_code::solution!(2);
+
+fn is_safe(data: &Vec<u32>) -> bool {
+    let mut previous_direction = None;
+    for i in 0..(data.len() - 1) {
+        let diff = data[i].abs_diff(data[i + 1]);
+        if diff > 3 {
+            return false;
+        }
+        let direction = data[i].cmp(&data[i + 1]);
+        match previous_direction {
+            Some(previous_direction) => if previous_direction != direction {
+                return false;
+            },
+            None => previous_direction = Some(direction)
+        }
+    }
+    true
+}
+
+fn is_safe_lenient(data: &Vec<u32>) -> bool {
+    if is_safe(data) {
+        return true;
+    }
+    for i in 0..data.len() {
+        let mut modified_data = data.clone();
+        modified_data.remove(i);
+        if is_safe(&modified_data) {
+            return true
+        }
+    }
+    false
+}
+
+fn count_safe_reports<P>(input: &str, predicate: P) -> u32
+where
+    P: FnMut(&Vec<u32>) -> bool
+{
+    input.lines()
+        .map(|line| line.split_whitespace()
+            .map(|number| number.parse::<u32>().unwrap())
+            .collect::<Vec<u32>>())
+        .filter(predicate)
+        .count() as u32
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    Some(count_safe_reports(input, is_safe))
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    Some(count_safe_reports(input, is_safe_lenient))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(2));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(4));
+    }
+}