that *should* be day 9, and the example passes,

but the real input is off!!!

aoc_libs/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "aoc_libs"
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+description.workspace = true

aoc_libs/src/lib.rs

@@ -0,0 +1 @@
+pub mod points;

aoc_libs/src/points.rs

@@ -0,0 +1,211 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Hash)]
+pub struct Point {
+    pub x: isize,
+    pub y: isize,
+}
+
+impl Point {
+    /// converts a point (representing a point on a 4 quadrant grid with positive xy in the
+    /// top-right) into a upoint (representing a point on a 1 quadrant grid with the origin in the
+    /// top-left corner). Returns none if the resulting point would have either number negative.
+    pub fn to_upoint(self, zero_coord: &UPoint) -> Option<UPoint> {
+        Some(UPoint {
+            x: zero_coord.x.checked_add_signed(self.x)?,
+            y: zero_coord.y.checked_add_signed(-self.y)?,
+        })
+    }
+}
+
+impl std::ops::Add for Point {
+    type Output = Point;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Self {
+            x: self.x + rhs.x,
+            y: self.y + rhs.y,
+        }
+    }
+}
+
+impl std::ops::AddAssign for Point {
+    fn add_assign(&mut self, rhs: Self) {
+        *self = *self + rhs
+    }
+}
+
+impl std::ops::Sub for Point {
+    type Output = Point;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Self {
+            x: self.x - rhs.x,
+            y: self.y - rhs.y,
+        }
+    }
+}
+
+impl std::ops::SubAssign for Point {
+    fn sub_assign(&mut self, rhs: Self) {
+        *self = *self - rhs
+    }
+}
+
+impl std::ops::Neg for Point {
+    type Output = Point;
+
+    fn neg(self) -> Self::Output {
+        Point {
+            x: -self.x,
+            y: -self.y,
+        }
+    }
+}
+
+/// an unsigned point in 2d space
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct UPoint {
+    pub x: usize,
+    pub y: usize,
+}
+
+impl UPoint {
+    /// converts a upoint (representing a point on a 1 quadrant grid with the origin in the
+    /// top-left corner) into a point( representing a point on a 4 quadrant grid with positive xy
+    /// in the top-right)
+    pub fn to_point(self, zero_coord: &UPoint) -> Point {
+        Point {
+            x: -(zero_coord.x as isize - self.x as isize),
+            y: zero_coord.y as isize - self.y as isize,
+        }
+    }
+}
+
+impl std::ops::Add for UPoint {
+    type Output = UPoint;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Self {
+            x: self.x + rhs.x,
+            y: self.y + rhs.y,
+        }
+    }
+}
+
+impl std::ops::AddAssign for UPoint {
+    fn add_assign(&mut self, rhs: Self) {
+        *self = *self + rhs
+    }
+}
+
+impl std::ops::Sub for UPoint {
+    type Output = UPoint;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Self {
+            x: self.x - rhs.x,
+            y: self.y - rhs.y,
+        }
+    }
+}
+
+impl std::ops::SubAssign for UPoint {
+    fn sub_assign(&mut self, rhs: Self) {
+        *self = *self - rhs
+    }
+}
+
+/// A matrix that allows negative co-oordinates. Will panic if referencing out of bounds, just like
+/// a normal 2d array.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct FourQuadrantMatrix<const X: usize, const Y: usize, T> {
+    matrix: [[T; X]; Y],
+    max_point: Point,
+    min_point: Point,
+    zero_coord: UPoint,
+}
+
+impl<const X: usize, const Y: usize, T> FourQuadrantMatrix<{ X }, { Y }, T>
+where
+    T: Copy,
+    T: Default,
+{
+    /// generates a new FourQuadrantMatrix with a given zero point (the point in the underlying 2d
+    /// array considered to be (0,0))
+    pub fn new(zero_coord: UPoint) -> FourQuadrantMatrix<{ X }, { Y }, T> {
+        FourQuadrantMatrix {
+            matrix: [[T::default(); X]; Y],
+            max_point: UPoint { x: X - 1, y: 0 }.to_point(&zero_coord),
+            min_point: UPoint { x: 0, y: Y - 1 }.to_point(&zero_coord),
+            zero_coord,
+        }
+    }
+
+    pub fn zero_coord(&self) -> UPoint {
+        self.zero_coord
+    }
+
+    pub fn min_point(&self) -> Point {
+        self.min_point
+    }
+
+    pub fn max_point(&self) -> Point {
+        self.max_point
+    }
+
+    /// makes sure a point is in bounds and if not, brings it in bounds.
+    pub fn bound_point(&self, point: &mut Point) {
+        if point.x > self.max_point.x {
+            point.x = self.max_point.x
+        }
+
+        if point.y > self.max_point.y {
+            point.y = self.max_point.y
+        }
+
+        if point.x < self.min_point.x {
+            point.x = self.min_point.x
+        }
+
+        if point.y < self.min_point.y {
+            point.y = self.min_point.y
+        }
+    }
+
+    /// checks if the point is in bounds.
+    pub fn is_in_bounds(&self, point: &Point) -> bool {
+        point.x <= self.max_point.x
+            && point.y <= self.max_point.y
+            && point.x >= self.min_point.x
+            && point.y >= self.min_point.y
+    }
+    /// fills the matrix with the Ts default value.
+    pub fn reset_matrix(&mut self) {
+        self.matrix = [[T::default(); X]; Y];
+    }
+}
+
+impl<T, const X: usize, const Y: usize> std::ops::IndexMut<Point> for FourQuadrantMatrix<{ X }, { Y }, T> {
+    fn index_mut(&mut self, index: Point) -> &mut Self::Output {
+        let upoint = index
+            .to_upoint(&self.zero_coord)
+            .expect("would result in negative unsigned coordinate!");
+        &mut self.matrix[upoint.y][upoint.x]
+    }
+}
+
+impl<T, const X: usize, const Y: usize> std::ops::Index<Point> for FourQuadrantMatrix<{ X }, { Y }, T> {
+    type Output = T;
+
+    fn index(&self, index: Point) -> &Self::Output {
+        let upoint = index
+            .to_upoint(&self.zero_coord)
+            .expect("would result in negative unsigned coordinate!");
+        &self.matrix[upoint.y][upoint.x]
+    }
+}
+
+impl<T, const X: usize, const Y: usize> From<FourQuadrantMatrix<{ X }, { Y }, T>> for [[T; X]; Y] {
+    fn from(value: FourQuadrantMatrix<{ X }, { Y }, T>) -> Self {
+        value.matrix
+    }
+}