feat: add day 4 - part 2

day_4/src/lib.rs

@@ -1,6 +1,7 @@
+use std::cmp;
 use std::str::FromStr;
 
-#[derive(Debug, Default, PartialEq)]
+#[derive(Debug, Default, PartialEq, Clone)]
 pub struct CardNumbers {
     pub numbers: Vec<u32>,
 }
@@ -41,11 +42,10 @@ impl FromStr for CardNumbers {
     }
 }
 
-#[derive(Debug, Default, PartialEq)]
+#[derive(Debug, Default, PartialEq, Clone)]
 pub struct Card {
     pub id: usize,
-    pub winning_numbers: CardNumbers,
-    pub owned_numbers: CardNumbers,
+    pub winning_numbers_count: usize,
 }
 
 impl FromStr for Card {
@@ -66,8 +66,7 @@ impl FromStr for Card {
     /// let string = "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53";
     /// let expected_result = Card {
     ///     id: 1,
-    ///     winning_numbers: CardNumbers { numbers: vec![41, 48, 83, 86, 17], },
-    ///     owned_numbers: CardNumbers { numbers: vec![83, 86, 6, 31, 17, 9, 48, 53], },
+    ///     winning_numbers_count: 4,
     /// };
     /// let actual_result = Card::from_str(string).unwrap();
     ///
@@ -81,16 +80,23 @@ impl FromStr for Card {
             .unwrap_or("Card 1")
             .strip_prefix("Card ")
             .unwrap_or("1")
+            .trim()
             .parse()
             .unwrap_or(1);
 
         let mut numbers_parts = parts.next().unwrap_or("").split(" | ");
 
-        result.winning_numbers =
+        let winning_numbers =
             CardNumbers::from_str(numbers_parts.next().unwrap_or("")).unwrap_or_default();
-        result.owned_numbers =
+        let owned_numbers =
             CardNumbers::from_str(numbers_parts.next().unwrap_or("")).unwrap_or_default();
 
+        result.winning_numbers_count = owned_numbers
+            .numbers
+            .iter()
+            .filter(|&owned_number| winning_numbers.numbers.contains(owned_number))
+            .count();
+
         Ok(result)
     }
 }
@@ -100,15 +106,10 @@ pub fn part_1(input: &str) -> usize {
         .lines()
         .map(|line| Card::from_str(line).unwrap_or_default())
         .map(|card| {
-            let numbers_matches_count = card
-                .owned_numbers
-                .numbers
-                .iter()
-                .filter(|&owned_number| card.winning_numbers.numbers.contains(owned_number))
-                .count() as u32;
+            let winning_numbers_count = card.winning_numbers_count as u32;
             let base: usize = 2;
-            if numbers_matches_count > 0 {
-                base.pow(numbers_matches_count.saturating_sub(1))
+            if winning_numbers_count > 0 {
+                base.pow(winning_numbers_count.saturating_sub(1))
             } else {
                 0
             }
@@ -116,6 +117,36 @@ pub fn part_1(input: &str) -> usize {
         .sum::<usize>()
 }
 
+pub fn part_2(input: &str) -> usize {
+    let cards = input
+        .lines()
+        .map(|line| Card::from_str(line).unwrap_or_default())
+        .collect::<Vec<Card>>();
+    let mut cards_identifiers = cards.iter().map(|card| card.id).collect::<Vec<usize>>();
+
+    let mut index_card = 0;
+    loop {
+        if index_card >= cards_identifiers.len() {
+            break;
+        }
+
+        if let Some(card) = cards.get(cards_identifiers.get(index_card).unwrap_or(&0) - 1) {
+            let card_position_index = card.id - 1;
+            let maximum_index = cmp::min(
+                card_position_index + card.winning_numbers_count,
+                cards.len() - 1,
+            );
+            for index in card_position_index + 1..=maximum_index {
+                cards_identifiers.push(index + 1);
+            }
+        }
+
+        index_card += 1;
+    }
+
+    cards_identifiers.len()
+}
+
 #[cfg(test)]
 mod day_4_tests {
     use super::*;
@@ -125,8 +156,8 @@ mod day_4_tests {
         assert_eq!(part_1(include_str!("../input_example_1.txt")), 13);
     }
 
-    // #[test]
-    // fn test_part_2_example() {
-    //     assert_eq!(part_2(include_str!("../input_example_1.txt")), 467835);
-    // }
+    #[test]
+    fn test_part_2_example() {
+        assert_eq!(part_2(include_str!("../input_example_1.txt")), 30);
+    }
 }

day_4/src/main.rs

@@ -1,8 +1,8 @@
-use day_4::part_1;
+use day_4::{part_1, part_2};
 
 fn main() {
     let input = include_str!("../input.txt");
     println!("- Day 4: Scratchcards -");
     println!("Answer Part 1: {}", part_1(input));
-    // println!("Answer Part 2: {}", part_2(input));
+    println!("Answer Part 2: {}", part_2(input));
 }