day(04): add initial solution

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

samples/day04.txt

@@ -0,0 +1,6 @@
+2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8

src/bin/day04.rs

@@ -0,0 +1,99 @@
+use std::ops::{Range, RangeInclusive};
+use std::str::FromStr;
+use std::{collections::HashSet, ops::RangeBounds};
+
+use aoc_2022::*;
+
+use color_eyre::eyre::{Report, Result};
+use tracing::*;
+use tracing_subscriber::EnvFilter;
+
+struct Assignment(RangeInclusive<i32>, RangeInclusive<i32>);
+
+impl FromStr for Assignment {
+    type Err = Report;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let split_s = s.split(',').collect::<Vec<_>>();
+        let (left, right) = (split_s[0], split_s[1]);
+
+        let (l_split, r_split) = (
+            left.split('-').collect::<Vec<_>>(),
+            right.split('-').collect::<Vec<_>>(),
+        );
+        let (l_min, l_max) = (l_split[0], l_split[1]);
+        let (r_min, r_max) = (r_split[0], r_split[1]);
+
+        let (ll, lu) = (l_min.parse::<i32>()?, l_max.parse::<i32>()?);
+        let (rl, ru) = (r_min.parse::<i32>()?, r_max.parse::<i32>()?);
+
+        // debug!("Parsed: {}..={}, {}..={}", ll, lu, rl, ru);
+
+        Ok(Assignment(ll..=lu, rl..=ru))
+    }
+}
+
+type Input = Vec<Assignment>;
+type Output = i32;
+
+fn part_1(input: &Input) -> Output {
+    input
+        .iter()
+        .filter(|Assignment(l, r)| {
+            (l.start() <= r.start() && r.end() <= l.end())
+                || (r.start() <= l.start() && l.end() <= r.end())
+        })
+        .count() as i32
+}
+
+fn part_2(input: &Input) -> Output {
+    input
+        .iter()
+        .filter(|Assignment(l, r)| {
+            l.contains(r.start())
+                || l.contains(r.end())
+                || r.contains(l.start())
+                || r.contains(l.end())
+        })
+        .count() as i32
+}
+
+fn parse_input(pathname: &str) -> Input {
+    file_to_structs(pathname)
+}
+
+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/day04.txt");
+
+    info!("Part 1: {}", part_1(&input));
+    info!("Part 2: {}", part_2(&input));
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod day_04 {
+    use super::*;
+
+    #[test]
+    fn test_part_1() {
+        let sample = parse_input("samples/day04.txt");
+        assert_eq!(part_1(&sample), 2);
+    }
+
+    #[test]
+    fn test_part_2() {
+        let sample = parse_input("samples/day04.txt");
+        assert_eq!(part_2(&sample), 4);
+    }
+}