From b0257b30584a6a9da6d1cd1eee4219ccdbfa464a Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Mon, 4 Dec 2023 18:14:18 +0100
Subject: Add day4

---
 2023/day4/src/lib.rs | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 2023/day4/src/lib.rs

(limited to '2023/day4/src')

diff --git a/2023/day4/src/lib.rs b/2023/day4/src/lib.rs
new file mode 100644
index 0000000..cc3742a
--- /dev/null
+++ b/2023/day4/src/lib.rs
@@ -0,0 +1,128 @@
+fn parse(input: &str) -> Vec<String> {
+    input
+        .trim_end()
+        .split('\n')
+        .map(|x| {
+            let b = x.to_string();
+            let k = b.split(':').last().unwrap();
+
+            return k.trim().to_string();
+        })
+        .collect()
+}
+
+pub fn part1(input: &str) -> u32 {
+    let mut res: u32 = 0;
+
+    let cards: Vec<String> = parse(input);
+    for card in cards {
+        let numbers: Vec<String> = card.split('|').map(|x| x.trim().to_string()).collect();
+        assert_eq!(numbers.len(), 2);
+
+        let winnings: Vec<_> = numbers[0]
+            .replace("  ", " ")
+            .split(' ')
+            .map(|x| x.trim().parse::<u32>().unwrap())
+            .collect();
+        let plays: Vec<_> = numbers[1]
+            .replace("  ", " ")
+            .split(' ')
+            .map(|x| x.trim().parse::<u32>().unwrap())
+            .collect();
+
+        let mut k = 0;
+        for win in winnings {
+            if plays.contains(&win) {
+                k = if k == 0 { 1 } else { k * 2 };
+            }
+        }
+        res += k;
+    }
+
+    res
+}
+
+//
+//
+//
+// 1 -> 4 | x
+// 2 -> 2 | y x
+// 3 -> 2 | y y y x
+// 4 -> 1 | y y y y y y y x
+// 5 -> 0 | y y y y y y y y y y y y y x
+// 6 -> 0 | x
+//
+//
+pub fn part2(input: &str) -> u32 {
+    let mut res: u32 = 0;
+
+    let cards: Vec<String> = parse(input);
+    let mut incr: Vec<u32> = Vec::new();
+    incr.resize_with(cards.len(), Default::default);
+
+    let mut i = 0;
+    for card in cards {
+        let numbers: Vec<String> = card.split('|').map(|x| x.trim().to_string()).collect();
+        assert_eq!(numbers.len(), 2);
+
+        let winnings: Vec<_> = numbers[0]
+            .replace("  ", " ")
+            .split(' ')
+            .map(|x| x.trim().parse::<u32>().unwrap())
+            .collect();
+        let plays: Vec<_> = numbers[1]
+            .replace("  ", " ")
+            .split(' ')
+            .map(|x| x.trim().parse::<u32>().unwrap())
+            .collect();
+
+        let mut k = 0;
+        for win in winnings {
+            if plays.contains(&win) {
+                k += 1;
+            }
+        }
+
+        for j in i + 1..i + 1 + k {
+            incr[j] += 1 + incr[i];
+        }
+
+        res += 1 + incr[i];
+        i += 1;
+    }
+
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_part1() {
+        let input = include_str!("../example.txt");
+        let result = part1(input);
+        assert_eq!(result, 13);
+    }
+
+    #[test]
+    fn input_part1() {
+        let input = include_str!("../input.txt");
+        let result = part1(input);
+        assert_eq!(result, 25174);
+    }
+
+    #[test]
+    fn example_part2() {
+        let input = include_str!("../example.txt");
+        let result = part2(input);
+        assert_eq!(result, 30);
+    }
+
+    #[test]
+    fn input_part2() {
+        let input = include_str!("../input.txt");
+        let result = part2(input);
+        assert_eq!(result, 6420979);
+    }
+}
-- 
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