From 7f21e6d464f740f4a618c1baa6bb6a449759a5de Mon Sep 17 00:00:00 2001
From: Pascal Phelipot <pascal@phelipot.me>
Date: Mon, 4 Dec 2023 20:29:37 +0100
Subject: [PATCH] Day 4 part 2

---
 src/day4/mod.rs | 57 +++++++++++++++++++++++++++++++++++++++++--------
 src/main.rs     | 12 ++++++++---
 2 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/src/day4/mod.rs b/src/day4/mod.rs
index 9fba754..2ab87be 100644
--- a/src/day4/mod.rs
+++ b/src/day4/mod.rs
@@ -1,9 +1,13 @@
+use std::collections::VecDeque;
+
 use log::debug;
 
 use super::utils::Part;
 
 struct Card {
-    nb_winning: u32
+    nb_winning: u32,
+    value: u32,
+    count: u32
 }
 
 fn parse(line: &str) -> Card {
@@ -17,8 +21,10 @@ fn parse(line: &str) -> Card {
     debug!("{:?}", nb_card);
 
     let mut value = 0;
+    let mut winner_nb = 0;
     for nb in nb_card {
         if nb_win.contains(&nb) {
+            winner_nb += 1;
             if value == 0 {
                 value = 1;
             }else{
@@ -27,27 +33,60 @@ fn parse(line: &str) -> Card {
         }
     }
 
-    Card { nb_winning: value }
+    Card { nb_winning: winner_nb, value, count: 1 }
 }
 
 pub fn solve(lines: Vec<String>, part: Part) -> u32 {
-    let mut sum = 0;
-    for line in lines {
-        sum += parse(&line).nb_winning;
-    }
+    let mut cards : Vec<Card> = lines.iter().map(|l| parse(l)).collect();
 
-    sum
+
+    match part {
+        Part::One => cards.iter().map(|c| c.value).sum(),
+        Part::Two => {
+            let mut next_adds : VecDeque<u32> = VecDeque::new();
+            let mut counter = 0;
+            for card in &mut cards {
+                counter += 1;
+                debug!("Card {}: Adding {} next cards", counter, card.nb_winning);
+
+                if let Some(bonus) = next_adds.pop_front(){
+                    // If there is a value, we add it to the current card
+                    card.count += bonus;
+                    debug!("Current card count is {}", card.count);
+                }
+                for i in 0..(card.nb_winning) {
+                    // For each value our current card has we add all those on the stack
+                    if let Some(value) = next_adds.get_mut(i as usize){
+                        *value += card.count;
+                    }else{
+                        next_adds.push_back(card.count);
+                    }
+                }
+                debug!("Next bonus: {:?}", next_adds);
+            }
+
+            cards.iter().map(|c| c.count).sum()
+        }
+    }
 }
 
 #[cfg(test)]
 mod tests {
-    use super::parse;
+    use super::{parse, solve};
 
     #[test]
     fn test_line() {
         let line = "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53".to_owned();
 
         let card = parse(&line);
-        assert_eq!(card.nb_winning, 8);
+        assert_eq!(card.value, 8);
+    }
+
+    #[test]
+    fn test_part2(){
+        let lines = "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53\nCard 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19\nCard 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1\nCard 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83\nCard 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36\nCard 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11".to_owned();
+        let result =solve(lines.lines().map(|v| v.to_owned()).collect(), crate::utils::Part::Two);
+
+        assert_eq!(result, 30);
     }
 }
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 80412d7..deadbd3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,9 +17,6 @@ fn main() {
         .format_timestamp(None)
         .init();
 
-    let data_path = "./datasets/adventofcode.com_2023_day_4_input.txt";
-    let result = day4::solve(utils::lines_from_file(data_path).expect("Could not load the dataset for day 3"), Part::One);
-    info!("Result : {}", result);
 }
 
 
@@ -57,4 +54,13 @@ mod tests {
         assert_eq!(result, 522726);
         assert_eq!(result2, 81721933);
     }
+
+    #[test]
+    fn day4() {
+        let data_path = "./datasets/adventofcode.com_2023_day_4_input.txt";
+        let result = day4::solve(utils::lines_from_file(data_path).expect("Could not load the dataset for day 3"), Part::One);
+        let result2 = day4::solve(utils::lines_from_file(data_path).expect("Could not load the dataset for day 3"), Part::Two);
+        assert_eq!(result, 20407);
+        assert_eq!(result2, 23806951);
+    }
 }
\ No newline at end of file