Day 4 part 1

src/day04/input/test1.txt

@@ -0,0 +1,6 @@
+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

src/day04/mod.rs

@@ -0,0 +1,103 @@
+use std::{collections::HashSet, str::FromStr};
+
+use anyhow::{anyhow, Result};
+
+use crate::instrument::instrument;
+
+const INPUT: &str = include_str!("input/input.txt");
+
+#[derive(Debug)]
+struct Card {
+    winning_numbers: HashSet<u8>,
+    numbers: HashSet<u8>,
+    id: usize,
+}
+
+impl FromStr for Card {
+    type Err = anyhow::Error;
+    fn from_str(s: &str) -> Result<Self> {
+        let mut s = s.trim().split(':');
+        let id = s
+            .next()
+            .ok_or_else(|| anyhow!("Invalid card: no ':' found"))?;
+        let id = id
+            .split(' ')
+            .last()
+            .ok_or_else(|| anyhow!("Invalid card: no number found"))?
+            .parse()?;
+
+        let mut nums = s
+            .next()
+            .ok_or_else(|| anyhow!("Invalid card: nothing after ':' found"))?
+            .split('|');
+        let first_nums = nums
+            .next()
+            .ok_or_else(|| anyhow!("Invalid card: no '|' found"))?
+            .trim();
+
+        let winning_numbers = first_nums
+            .split_whitespace()
+            .map(|num| Ok(num.parse()?))
+            .collect::<Result<HashSet<u8>>>()?;
+        let second_nums = nums
+            .next()
+            .ok_or_else(|| anyhow!("Invalid card: nothing after '|' found"))?
+            .trim();
+        let numbers = second_nums
+            .split_whitespace()
+            .map(|num| Ok(num.parse()?))
+            .collect::<Result<HashSet<u8>>>()?;
+        Ok(Self {
+            winning_numbers,
+            numbers,
+            id,
+        })
+    }
+}
+
+impl Card {
+    fn score(&self) -> u32 {
+        let winning = self.winning_numbers.intersection(&self.numbers).count() as u32;
+        if winning == 0 {
+            0
+        } else {
+            2_u32.pow(winning.saturating_sub(1))
+        }
+    }
+}
+
+fn part1(input: &str) -> Result<u32> {
+    let mut sum = 0;
+    for card in input.trim().split('\n').map(|card| card.parse::<Card>()) {
+        let card = card?;
+        sum += card.score();
+    }
+    Ok(sum)
+}
+
+fn part2(input: &str) -> Result<u32> {
+    unimplemented!()
+}
+
+pub fn solve() -> Result<()> {
+    println!("\nDay 04");
+    instrument!(part1(INPUT)?, part2(INPUT)?);
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(TEST_INPUT1).unwrap(), 13);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(TEST_INPUT1).unwrap(), 0);
+    }
+}

src/main.rs

@@ -1,6 +1,7 @@
 pub mod day01;
 pub mod day02;
 pub mod day03;
+pub mod day04;
 pub mod instrument;
 
 use anyhow::Result;
@@ -10,6 +11,7 @@ fn main() -> Result<()> {
     day01::solve()?;
     day02::solve()?;
     day03::solve()?;
+    day04::solve()?;
 
     Ok(())
 }