day 15

2023/day15/src/lib.rs

@@ -0,0 +1,79 @@
+use helper::{Day, Variants};
+
+pub fn main() {
+    helper::main::<Day15>(include_str!("../input.txt"));
+}
+
+struct Day15;
+
+helper::define_variants! {
+    day => crate::Day15;
+    part1 {
+        basic => crate::part1;
+    }
+    part2 {
+        basic => crate::part2;
+    }
+}
+
+impl Day for Day15 {
+    fn part1() -> Variants {
+        part1_variants!(construct_variants)
+    }
+
+    fn part2() -> Variants {
+        part2_variants!(construct_variants)
+    }
+}
+
+fn part1(input: &str) -> u64 {
+    input.trim_end().split(",").map(hash).sum()
+}
+
+fn hash(s: &str) -> u64 {
+    s.bytes()
+        .fold(0, |state, b| ((state + u64::from(b)) * 17) % 256)
+}
+
+fn part2(input: &str) -> u64 {
+    let mut boxes = vec![Vec::<(&str, u64)>::new(); 256];
+
+    for step in input.trim_end().split(',') {
+        if let Some(label) = step.strip_suffix('-') {
+            let b = &mut boxes[hash(label) as usize];
+            b.retain(|lens| lens.0 != label);
+        } else {
+            let (label, number) = step.split_once("=").unwrap();
+            let number = number.parse().unwrap();
+            let b = &mut boxes[hash(label) as usize];
+            if let Some(existing) = b.iter().position(|lens| lens.0 == label) {
+                b[existing] = (label, number);
+            } else {
+                b.push((label, number));
+            }
+        }
+    }
+
+    boxes
+        .iter()
+        .enumerate()
+        .flat_map(|(box_idx, b)| {
+            b.iter().enumerate().map(move |(lens_idx, lens)| {
+                (1 + (box_idx as u64)) * ((lens_idx as u64) + 1) * lens.1
+            })
+        })
+        .sum()
+}
+
+helper::tests! {
+    day15 Day15;
+    part1 {
+        small => 1320;
+        default => 513643;
+    }
+    part2 {
+        small => 145;
+        default => 265345;
+    }
+}
+helper::benchmarks! {}

2023/day15/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    day15::main();
+}