solution: day 1

data/examples/01.txt

@@ -0,0 +1,6 @@
+3   4
+4   3
+2   5
+1   3
+3   9
+3   3

src/bin/01.rs

@@ -0,0 +1,57 @@
+use hashbrown::HashMap;
+use itertools::Itertools;
+
+fn parse_input(input: &str) -> impl Iterator<Item = (isize, isize)> + '_ {
+    input.lines().map(|l| {
+        l.split(' ')
+            .filter_map(|x| x.parse::<isize>().ok())
+            .collect_tuple()
+            .unwrap()
+    })
+}
+
+pub fn part_one(input: &str) -> Option<isize> {
+    let mut left = vec![];
+    let mut right = vec![];
+
+    for (a, b) in parse_input(input) {
+        left.push(a);
+        right.push(b);
+    }
+
+    left.sort();
+    right.sort();
+
+    Some(
+        left.into_iter()
+            .zip(right)
+            .map(|(x, y)| (x - y).abs())
+            .sum(),
+    )
+}
+
+pub fn part_two(input: &str) -> Option<isize> {
+    let mut map = HashMap::new();
+
+    for (a, b) in parse_input(input) {
+        map.entry(a).or_insert((0, 0)).0 += 1;
+        map.entry(b).or_insert((0, 0)).1 += 1;
+    }
+
+    Some(map.into_iter().map(|(k, v)| k * v.0 * v.1).sum())
+}
+
+aoc::solution!(1);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(part_one(&aoc::template::read_file("examples", 1)), Some(11));
+    }
+    #[test]
+    fn test_part_two() {
+        assert_eq!(part_two(&aoc::template::read_file("examples", 1)), Some(31));
+    }
+}