From 6f8d539c0c708e1c456066b127d0b3233c80ba8f Mon Sep 17 00:00:00 2001
From: Philippe Zwietering <philippe.zwietering@gmail.com>
Date: Mon, 4 Dec 2023 16:53:45 +0100
Subject: [PATCH] Finished day 4 aoc 2023, just in time for the end of the day

---
 advent_of_code/2023/4/src/main.rs | 44 ++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/advent_of_code/2023/4/src/main.rs b/advent_of_code/2023/4/src/main.rs
index 52db50b..091c7b1 100644
--- a/advent_of_code/2023/4/src/main.rs
+++ b/advent_of_code/2023/4/src/main.rs
@@ -1,3 +1,4 @@
+use std::cmp::min;
 use std::collections::HashSet;
 
 use nom::{
@@ -40,10 +41,37 @@ fn card_score(card: &(Vec<u32>, Vec<u32>)) -> u32 {
     }
 }
 
+fn card_wins(card: &(Vec<u32>, Vec<u32>)) -> u32 {
+    let winning_numbers: HashSet<&u32> = HashSet::from_iter(card.0.iter());
+
+    card.1
+        .iter()
+        .filter(|&number| winning_numbers.contains(number))
+        .count() as u32
+}
 fn solve_1(scratchcards: &[(Vec<u32>, Vec<u32>)]) -> u32 {
     scratchcards.iter().map(card_score).sum()
 }
 
+fn solve_2(scratchcards: &[(Vec<u32>, Vec<u32>)]) -> u32 {
+    let mut number_of_cards = vec![1; scratchcards.len()];
+
+    let card_wins = scratchcards.iter().map(card_wins).collect::<Vec<_>>();
+
+    for card_number in 0..scratchcards.len() {
+        for winner_card_numbers in (card_number + 1)
+            ..min(
+                scratchcards.len(),
+                card_number + 1 + card_wins[card_number] as usize,
+            )
+        {
+            number_of_cards[winner_card_numbers] += number_of_cards[card_number];
+        }
+    }
+
+    number_of_cards.iter().sum()
+}
+
 fn main() {
     println!("Hello, this is Patrick!");
 
@@ -52,9 +80,14 @@ fn main() {
     let (_, scratchcards) = parse_input(input_txt).unwrap();
 
     println!(
-        "The scratch cards are worth {} points",
+        "The scratchcards are worth {} points",
         solve_1(&scratchcards[..])
     );
+
+    println!(
+        "The total number of scratchcards is {}",
+        solve_2(&scratchcards[..])
+    );
 }
 
 #[cfg(test)]
@@ -69,4 +102,13 @@ mod tests {
 
         assert_eq!(solve_1(&scratchcards[..]), 13);
     }
+
+    #[test]
+    fn test_2() {
+        let input_text = include_str!("../test_input.txt");
+
+        let (_, scratchcards) = parse_input(input_text).unwrap();
+
+        assert_eq!(solve_2(&scratchcards[..]), 30);
+    }
 }