Add day 3

AoC_2025/src/days/day03.rs

@@ -0,0 +1,53 @@
+use crate::days::Solution;
+
+pub struct Day03;
+
+impl Solution for Day03 {
+    type Input = Vec<Vec<u32>>;
+
+    fn parse(&self, data: &str) -> Self::Input {
+        data.split("\n")
+            .filter(|s| !s.is_empty())
+            .map(|s| s.chars().map(|c| c.to_digit(10).unwrap_or(0)).collect())
+            .collect()
+    }
+
+    fn part1(&self, input: &Self::Input) -> usize {
+        input
+            .iter()
+            .map(|l| {
+                let (i1, m1) = max(&l[..l.len() - 1]);
+                let (_, m2) = max(&l[i1 + 1..]);
+                10 * m1 + m2
+            })
+            .sum::<u32>() as usize
+    }
+
+    fn part2(&self, input: &Self::Input) -> usize {
+        println!("Part2");
+        input
+            .iter()
+            .map(|l| {
+                (0..12)
+                    .rfold((0, 0), |(start_index, joltage), n| {
+                        let (i, m) = max(&l[start_index..l.len() - n]);
+                        (
+                            start_index + i + 1,
+                            usize::pow(10, n as u32) * m as usize + joltage,
+                        )
+                    })
+                    .1
+            })
+            .sum()
+    }
+}
+
+fn max(l: &[u32]) -> (usize, u32) {
+    let x = l.iter().enumerate().fold(
+        (0, 0),
+        |(index_m, m), (i, &x)| if x > m { (i, x) } else { (index_m, m) },
+    );
+
+    println!("Max of {:?} is {:?}", l, x);
+    x
+}