Non-functional impl

2023/src/day24.rs

@@ -1,7 +1,82 @@
-pub fn part1(_input: &[u8]) -> anyhow::Result<String> {
-    anyhow::bail!("Not implemented")
+use nom::bytes::complete::tag;
+use nom::combinator::map;
+use nom::multi::many1;
+use nom::sequence::terminated;
+use nom::sequence::tuple;
+use nom::IResult;
+use num_integer::Integer;
+
+use crate::common::parse_input;
+
+struct Hail {
+    position: [i64; 3],
+    speed: [i64; 3],
+}
+
+impl Hail {
+    fn intersect(&self, other: &Self) -> bool {
+        // Assumption: speed in no coordinate is 0. This happens to be true.
+        let multiplier = self.speed[0].lcm(&self.speed[1]);
+
+        let mult_x = multiplier / self.speed[0];
+        let mult_y = multiplier / self.speed[1];
+
+        // use the formula for X
+        false
+    }
+
+    fn parse(i: &[u8]) -> IResult<&[u8], Self> {
+        use nom::character::complete::i64;
+        let parse_coordinates = |i| {
+            map(
+                tuple((terminated(i64, tag(", ")), terminated(i64, tag(", ")), i64)),
+                |(x, y, z)| [x, y, z],
+            )(i)
+        };
+
+        map(
+            tuple((
+                terminated(parse_coordinates, tag(" @ ")),
+                terminated(parse_coordinates, tag("\n")),
+            )),
+            |(position, speed)| Self { position, speed },
+        )(i)
+    }
+}
+fn parse_hail(i: &[u8]) -> IResult<&[u8], Vec<Hail>> {
+    many1(Hail::parse)(i)
+}
+
+pub fn part1(input: &[u8]) -> anyhow::Result<String> {
+    let hail = parse_input(input, parse_hail)?;
+
+    let intersections = hail
+        .iter()
+        .enumerate()
+        .flat_map(|(i, a)| {
+            hail[i + 1..]
+                .iter()
+                .map(move |b| (a, b))
+                .filter(|(a, b)| a.intersect(b))
+        })
+        .count();
+
+    Ok(intersections.to_string())
 }
 
 pub fn part2(_input: &[u8]) -> anyhow::Result<String> {
     anyhow::bail!("Not implemented")
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/24.txt");
+
+    #[test]
+    #[ignore = "not completely implemented"]
+    fn sample_part1() {
+        assert_eq!("2", part1(SAMPLE).unwrap());
+    }
+}

2023/src/samples/24.txt

@@ -0,0 +1,5 @@
+19, 13, 30 @ -2,  1, -2
+18, 19, 22 @ -1, -1, -2
+20, 25, 34 @ -2, -2, -4
+12, 31, 28 @ -1, -2, -1
+20, 19, 15 @  1, -5, -3