day4 solution 1

1 files changed, 63 insertions, 0 deletions

diff --git a/src/bin/day4.rs b/src/bin/day4.rs
new file mode 100644
index 0000000..ffd5d0b
--- /dev/null
+++ b/src/bin/day4.rs
@@ -0,0 +1,63 @@
+use std::collections::HashSet;
+
+static DAY: u8 = 4;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", total_points(&input));
+    println!("{DAY}b: {}", 0);
+}
+
+struct Card {
+    winning_numbers: HashSet<u32>,
+    numbers_you_have: HashSet<u32>,
+}
+
+impl Card {
+    fn new(input: &str) -> Card {
+        let (_id, numbers) = input.split_once(": ").unwrap();
+        let (win, have) = numbers.split_once(" | ").unwrap();
+        let winning_numbers = win.split(' ')
+                                 .filter(|x| !x.is_empty())
+                                 .map(|x| x.parse().unwrap())
+                                 .collect::<HashSet<_>>();
+        let numbers_you_have = have.split(' ')
+                                   .filter(|x| !x.is_empty())
+                                   .map(|x| x.parse().unwrap())
+                                   .collect::<HashSet<_>>();
+        Card { winning_numbers, numbers_you_have }
+    }
+
+    fn matching_numbers(&self) -> HashSet<u32> {
+        self.winning_numbers.intersection(&self.numbers_you_have).copied().collect()
+    }
+
+    fn points(&self) -> u32 {
+        (1 << self.matching_numbers().len()) / 2
+    }
+}
+
+fn total_points(input: &[String]) -> u32 {
+    input.iter()
+         .map(|x| Card::new(x))
+         .map(|c| c.points())
+         .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53",
+            "Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19",
+            "Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1",
+            "Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83",
+            "Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36",
+            "Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11",
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+        assert_eq!(total_points(&input), 13);
+    }
+}