Implement 2022 day 4

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 +1,89 @@
 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::minmax;
+use crate::common::parse_input;
+
+#[derive(Copy, Clone, PartialOrd, PartialEq)]
+struct Assignment(u32, u32);
+
+impl Assignment {
+    fn one_contains(self, other: Self) -> bool {
+        let (first, second) = minmax(self, other);
+
+        if second.0 == first.0 {
+            first.1 <= second.1
+        } else {
+            second.0 <= first.1 && second.1 <= first.1
+        }
+    }
+
+    fn one_overlaps(self, other: Self) -> bool {
+        let (first, second) = minmax(self, other);
+
+        if second.0 == first.0 {
+            first.1 <= second.1
+        } else {
+            second.0 <= first.1
+        }
+    }
 }
 
-pub fn part2(_input: &[u8]) -> Result<String> {
-    todo!()
+fn parse_assignments(input: &[u8]) -> IResult<&[u8], Vec<(Assignment, Assignment)>> {
+    use nom::character::complete::u32;
+
+    fn parse_single(input: &[u8]) -> IResult<&[u8], Assignment> {
+        map(separated_pair(u32, tag("-"), u32), |(start, end)| {
+            Assignment(start, end)
+        })(input)
+    }
+
+    let parse_line = separated_pair(parse_single, tag(","), parse_single);
+
+    many0(terminated(parse_line, newline))(input)
+}
+
+pub fn part1(input: &[u8]) -> Result<String> {
+    let assigments = parse_input(input, parse_assignments)?;
+
+    let overlapping = assigments
+        .into_iter()
+        .filter(|&(a, b)| a.one_contains(b))
+        .count();
+
+    Ok(overlapping.to_string())
+}
+
+pub fn part2(input: &[u8]) -> Result<String> {
+    let assigments = parse_input(input, parse_assignments)?;
+
+    let overlapping = assigments
+        .into_iter()
+        .filter(|&(a, b)| a.one_overlaps(b))
+        .count();
+
+    Ok(overlapping.to_string())
+}
+
+#[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