day9: part1 and bruteforce part 2 (some cleanups and clippies)

utils/grid/lib.rs

@@ -22,22 +22,37 @@ pub const ADJACENT_OFFSETS: [&(i64, i64); 8] = [
 /// NESW
 pub const CARDINAL_OFFSETS: [&(i64, i64); 4] = [&(0, -1), &(-1, 0), &(1, 0), &(0, 1)];
 
-#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
 pub struct Coord2d {
     pub x: i64,
     pub y: i64,
 }
 
-impl Debug for Coord2d {
+impl Display for Coord2d {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         f.write_fmt(format_args!("({}, {})", self.x, self.y))
     }
 }
 
+impl FromStr for Coord2d {
+    type Err = Box<dyn std::error::Error>;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let (l, r) = s.split_once(',').ok_or("Can't split on ,")?;
+        Ok(Coord2d {
+            x: l.parse()?,
+            y: r.parse()?,
+        })
+    }
+}
+
 pub trait AsCoord2d {
     fn to_coord(self) -> Coord2d;
     fn x(&self) -> i64;
     fn y(&self) -> i64;
+
+    fn manhattan<T: AsCoord2d>(&self, other: &T) -> u64 {
+        self.x().abs_diff(other.x()) + self.y().abs_diff(other.y())
+    }
 }
 
 impl<T: AsCoord2d> Sub<T> for &Coord2d {