day(03): add initial solution

Signed-off-by: Matej Focko <mfocko@redhat.com>

samples/day03.txt

@@ -0,0 +1,6 @@
+vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw

src/bin/day03.rs

@@ -0,0 +1,95 @@
+use std::collections::HashSet;
+
+use aoc_2022::*;
+
+use color_eyre::eyre::Result;
+use tracing::*;
+use tracing_subscriber::EnvFilter;
+
+type Input = Vec<(HashSet<i32>, HashSet<i32>)>;
+type Output = i32;
+
+fn part_1(input: &Input) -> Output {
+    input
+        .iter()
+        .map(|(left, right)| left.intersection(right).sum::<i32>())
+        .sum()
+}
+
+fn part_2(input: &Input) -> Output {
+    input
+        .iter()
+        .map(|(left, right)| left.union(right).cloned().collect())
+        .collect::<Vec<HashSet<i32>>>()
+        .chunks(3)
+        .map(|sets| {
+            // debug!("Sets: {:?}", sets);
+            sets.iter()
+                .skip(1)
+                .fold(sets[0].clone(), |acc, s| {
+                    acc.intersection(s).cloned().collect()
+                })
+                .iter()
+                .fold(0, |acc, x| acc + *x)
+        })
+        .sum()
+}
+
+fn parse_input(pathname: &str) -> Input {
+    file_to_lines(pathname)
+        .iter()
+        .map(|line| {
+            let mut left: HashSet<i32> = HashSet::new();
+            let mut right: HashSet<i32> = HashSet::new();
+
+            let mid = line.len() / 2;
+            for (i, c) in line.chars().enumerate() {
+                let s = if i < mid { &mut left } else { &mut right };
+
+                s.insert(if c < 'a' {
+                    c as i32 - 'A' as i32 + 27
+                } else {
+                    c as i32 - 'a' as i32 + 1
+                });
+            }
+
+            (left, right)
+        })
+        .collect()
+}
+
+fn main() -> Result<()> {
+    tracing_subscriber::fmt()
+        .with_env_filter(EnvFilter::from_default_env())
+        .with_target(false)
+        .with_file(true)
+        .with_line_number(true)
+        .without_time()
+        .compact()
+        .init();
+    color_eyre::install()?;
+
+    let input = parse_input("inputs/day03.txt");
+
+    info!("Part 1: {}", part_1(&input));
+    info!("Part 2: {}", part_2(&input));
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_1() {
+        let sample = parse_input("samples/day03.txt");
+        assert_eq!(part_1(&sample), 157);
+    }
+
+    #[test]
+    fn test_part_2() {
+        let sample = parse_input("samples/day03.txt");
+        assert_eq!(part_2(&sample), 70);
+    }
+}