Reimplement day 4 2022 with ranges instead of ints

2022/benches/days.rs

@@ -8,7 +8,7 @@ use criterion::BenchmarkId;
 use criterion::Criterion;
 
 /// Number of days we have an implementation to benchmark
-const DAYS_IMPLEMENTED: u8 = 3;
+const DAYS_IMPLEMENTED: u8 = 4;
 
 fn read_input(day: u8) -> Vec<u8> {
     let input_path = format!("inputs/{:02}.txt", day);

2022/src/common.rs

@@ -92,3 +92,15 @@ where
         }
     }
 }
+
+/// Return the minimum and maximum of two unordered variables
+pub fn minmax<T>(a: T, b: T) -> (T, T)
+where
+    T: PartialOrd,
+{
+    if a < b {
+        (a, b)
+    } else {
+        (b, a)
+    }
+}

2022/src/day04.rs

@@ -1,9 +1,75 @@
+use std::ops::RangeInclusive;
+
 use anyhow::Result;
+use nom::bytes::complete::tag;
+use nom::character::complete::newline;
+use nom::combinator::map;
+use nom::multi::many0;
+use nom::sequence::separated_pair;
+use nom::sequence::terminated;
+use nom::IResult;
 
-pub fn part1(_input: &[u8]) -> Result<String> {
-    todo!()
+use crate::common::parse_input;
+
+type Assignment = RangeInclusive<u32>;
+
+fn parse_assignments(
+    input: &[u8],
+) -> IResult<&[u8], Vec<(RangeInclusive<u32>, RangeInclusive<u32>)>> {
+    use nom::character::complete::u32;
+
+    fn parse_single(input: &[u8]) -> IResult<&[u8], Assignment> {
+        map(separated_pair(u32, tag("-"), u32), |(start, end)| {
+            start..=end
+        })(input)
+    }
+
+    let parse_line = separated_pair(parse_single, tag(","), parse_single);
+
+    many0(terminated(parse_line, newline))(input)
 }
 
-pub fn part2(_input: &[u8]) -> Result<String> {
-    todo!()
+fn is_contained(a: &Assignment, b: &Assignment) -> bool {
+    if a.size_hint().0 > b.size_hint().0 {
+        a.contains(b.start()) && a.contains(b.end())
+    } else {
+        b.contains(a.start()) && b.contains(a.end())
+    }
+}
+
+fn is_overlapping(a: &Assignment, b: &Assignment) -> bool {
+    b.end() >= a.start() && b.start() <= a.end() || a.end() >= b.start() && a.start() <= b.end()
+}
+
+fn parts_common(input: &[u8], filter: impl Fn(&Assignment, &Assignment) -> bool) -> Result<String> {
+    let assigments = parse_input(input, parse_assignments)?;
+
+    let overlapping = assigments.into_iter().filter(|(a, b)| filter(a, b)).count();
+
+    Ok(overlapping.to_string())
+}
+
+pub fn part1(input: &[u8]) -> Result<String> {
+    parts_common(input, is_contained)
+}
+
+pub fn part2(input: &[u8]) -> Result<String> {
+    parts_common(input, is_overlapping)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/04.txt");
+
+    #[test]
+    fn sample_part1() {
+        assert_eq!(part1(SAMPLE).unwrap(), "2")
+    }
+
+    #[test]
+    fn sample_part2() {
+        assert_eq!(part2(SAMPLE).unwrap(), "4")
+    }
 }

2022/src/samples/04.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