Solve day 04, part one

data/examples/04.txt

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+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/bin/04.rs

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+advent_of_code::solution!(4);
+
+// Count the number of winning card in hand
+fn count_winning(winning: Vec<&str>, hand: Vec<&str>) -> u32 {
+    let mut counter = 0;
+    winning.iter().for_each(|i| {
+        hand.iter().for_each(|j| {
+            if *i == *j {
+                counter += 1;
+            }
+        });
+    });
+    counter
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    input
+        .lines()
+        .map(|line| {
+            let input_line: Vec<_> = line.split(": ").collect();
+            let numbers: Vec<_> = input_line[1].split(" | ").collect();
+
+            let winning: Vec<&str> = numbers[0].split_whitespace().collect();
+            let hand: Vec<&str> = numbers[1].split_whitespace().collect();
+
+            let count = count_winning(winning, hand);
+            let points = match count {
+                0 => 0,
+                _ => 1 << count - 1, // Double by every winning card
+            };
+
+            points
+        })
+        .sum::<u32>()
+        .try_into()
+        .ok()
+}
+
+pub fn part_two(_input: &str) -> Option<u32> {
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(13));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}