From 4431b8746dcac9325c053eb28dc006bf59f8440e Mon Sep 17 00:00:00 2001
From: Lucas Resch <lucas.resch@gmx.de>
Date: Mon, 4 Dec 2023 08:47:14 +0100
Subject: [PATCH] 2023-04: Solve first puzzle

---
 2023-rust/data/examples/04.txt |  6 +++
 2023-rust/src/bin/04.rs        | 72 ++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 2023-rust/data/examples/04.txt
 create mode 100644 2023-rust/src/bin/04.rs

diff --git a/2023-rust/data/examples/04.txt b/2023-rust/data/examples/04.txt
new file mode 100644
index 0000000..9bdb874
--- /dev/null
+++ b/2023-rust/data/examples/04.txt
@@ -0,0 +1,6 @@
+Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
+Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
+Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
+Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
+Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
+Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
diff --git a/2023-rust/src/bin/04.rs b/2023-rust/src/bin/04.rs
new file mode 100644
index 0000000..2299df5
--- /dev/null
+++ b/2023-rust/src/bin/04.rs
@@ -0,0 +1,72 @@
+use itertools::Itertools;
+
+advent_of_code::solution!(4);
+
+struct ScratchCard {
+    index: u32,
+    winning_numbers: Vec<u32>,
+    numbers: Vec<u32>,
+}
+
+impl ScratchCard {
+    pub fn points(&self) -> u32 {
+        let fold = self
+            .winning_numbers
+            .iter()
+            .map(|number| self.numbers.contains(number))
+            .filter(|contained| *contained)
+            .fold(1, |acc, _| acc * 2);
+        fold / 2
+    }
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    parse_input(input)
+        .iter()
+        .map(|card| card.points())
+        .reduce(|acc, points| acc + points)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    None
+}
+
+fn parse_input(input: &str) -> Vec<ScratchCard> {
+    input
+        .lines()
+        .filter_map(|line| line.strip_prefix("Card"))
+        .filter_map(|line| line.split_once(':'))
+        .map(|(index, numbers)| {
+            let (winning, mine) = numbers.split_once('|').unwrap();
+            ScratchCard {
+                index: index.trim().parse().unwrap(),
+                winning_numbers: parse_numbers(winning),
+                numbers: parse_numbers(mine),
+            }
+        })
+        .collect_vec()
+}
+
+fn parse_numbers(numbers: &str) -> Vec<u32> {
+    numbers
+        .split_whitespace()
+        .map(|number| number.parse().unwrap())
+        .collect_vec()
+}
+
+#[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(13));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}