From 8cd0d842f0ffb0750f2df7dcee8c29c800d7c8af Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Mon, 4 Dec 2023 02:52:50 -0500
Subject: day 4

---
 src/bin/2023/day4.rs | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/bin/2023/main.rs |  2 ++
 2 files changed, 60 insertions(+)
 create mode 100644 src/bin/2023/day4.rs

(limited to 'src/bin')

diff --git a/src/bin/2023/day4.rs b/src/bin/2023/day4.rs
new file mode 100644
index 0000000..a93a1d2
--- /dev/null
+++ b/src/bin/2023/day4.rs
@@ -0,0 +1,58 @@
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+use advent_of_code::prelude::*;
+
+pub fn parse(fh: File) -> Result<Vec<(HashSet<i64>, HashSet<i64>)>> {
+    Ok(parse::raw_lines(fh)
+        .map(|line| {
+            let line = line.split(": ").nth(1).unwrap();
+            let mut parts = line.split(" | ");
+            let winning = parts.next().unwrap();
+            let ours = parts.next().unwrap();
+            (
+                winning
+                    .split_whitespace()
+                    .map(|s| s.parse().unwrap())
+                    .collect(),
+                ours.split_whitespace()
+                    .map(|s| s.parse().unwrap())
+                    .collect(),
+            )
+        })
+        .collect())
+}
+
+pub fn part1(cards: Vec<(HashSet<i64>, HashSet<i64>)>) -> Result<i64> {
+    let mut total = 0;
+    for (winning, ours) in cards {
+        let matches = (&ours & &winning).len();
+        if matches > 0 {
+            total += 2i64.pow((matches - 1).try_into().unwrap());
+        }
+    }
+    Ok(total)
+}
+
+pub fn part2(cards: Vec<(HashSet<i64>, HashSet<i64>)>) -> Result<i64> {
+    let mut counts = vec![1; cards.len()];
+    for (i, (winning, ours)) in cards.into_iter().enumerate() {
+        let matches = (&ours & &winning).len();
+        for prize in 0..matches {
+            counts[i + 1 + prize] += counts[i];
+        }
+    }
+    Ok(counts.iter().sum())
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2023, 4).unwrap()).unwrap()).unwrap(),
+        25183
+    );
+    assert_eq!(
+        part2(parse(parse::data(2023, 4).unwrap()).unwrap()).unwrap(),
+        5667240
+    );
+}
diff --git a/src/bin/2023/main.rs b/src/bin/2023/main.rs
index 652bf26..4033702 100644
--- a/src/bin/2023/main.rs
+++ b/src/bin/2023/main.rs
@@ -14,6 +14,7 @@ use advent_of_code::prelude::*;
 mod day1;
 mod day2;
 mod day3;
+mod day4;
 // NEXT MOD
 
 #[paw::main]
@@ -23,6 +24,7 @@ fn main(opt: Opt) -> Result<()> {
         1 => advent_of_code::day!(2023, opt.day, opt.puzzle, day1),
         2 => advent_of_code::day!(2023, opt.day, opt.puzzle, day2),
         3 => advent_of_code::day!(2023, opt.day, opt.puzzle, day3),
+        4 => advent_of_code::day!(2023, opt.day, opt.puzzle, day4),
         // NEXT PART
         _ => panic!("unknown day {}", opt.day),
     }
-- 
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