2023 day4/rust: add solution

2023/day4/rust/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "rust_2023_04"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aoc = { path = "../../../common/rust" }

2023/day4/rust/src/main.rs

@@ -0,0 +1,69 @@
+#![warn(clippy::pedantic)]
+
+use std::{io::stdin, num::NonZeroU32};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Card {
+    winning: Vec<usize>,
+    found: Vec<usize>,
+}
+
+impl Card {
+    pub fn parse(s: &str) -> Self {
+        fn get_numbers(s: &str) -> Vec<usize> {
+            s.split(' ')
+                .filter(|s| !s.is_empty())
+                .map(|n| n.parse().unwrap())
+                .collect()
+        }
+
+        let (_id, numbers) = s.split_once(": ").unwrap();
+        let (winning, found) = numbers.split_once(" | ").unwrap();
+        let winning = get_numbers(winning);
+        let found = get_numbers(found);
+
+        Self { winning, found }
+    }
+
+    pub fn num_matching(&self) -> usize {
+        self.found
+            .iter()
+            .filter(|n| self.winning.contains(n))
+            .count()
+    }
+
+    pub fn exp_score(&self) -> usize {
+        if let Some(matching) = NonZeroU32::new(u32::try_from(self.num_matching()).unwrap()) {
+            2_usize.pow(matching.get() - 1)
+        } else {
+            0
+        }
+    }
+
+    pub fn recursive_score(&self, previous: &[usize]) -> usize {
+        1 + previous
+            .iter()
+            .rev()
+            .take(self.num_matching())
+            .sum::<usize>()
+    }
+}
+
+fn main() {
+    let cards: Vec<Card> = stdin().lines().map(|l| Card::parse(&l.unwrap())).collect();
+
+    println!("{}", cards.iter().map(Card::exp_score).sum::<usize>());
+
+    let recursive_score: usize = cards
+        .iter()
+        .rev()
+        .fold(Vec::new(), |mut previous, card| {
+            let score = card.recursive_score(&previous);
+            previous.push(score);
+            previous
+        })
+        .iter()
+        .sum();
+
+    println!("{recursive_score}");
+}

Cargo.lock

@@ -663,6 +663,13 @@ dependencies = [
  "enum-map",
 ]
 
+[[package]]
+name = "rust_2023_04"
+version = "0.1.0"
+dependencies = [
+ "aoc",
+]
+
 [[package]]
 name = "rust_2023_05"
 version = "0.1.0"

Cargo.toml

@@ -29,5 +29,6 @@ members = [
 	"2022/day18/rust",
 	"2023/day1/rust",
 	"2023/day2/rust",
+	"2023/day4/rust",
 	"2023/day5/rust",
 ]