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

but the real input is off!!!

Cargo.lock

@@ -11,6 +11,10 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "aoc_libs"
+version = "0.1.0"
+
 [[package]]
 name = "day01"
 version = "0.1.0"
@@ -59,6 +63,9 @@ version = "0.1.0"
 [[package]]
 name = "day09"
 version = "0.1.0"
+dependencies = [
+ "aoc_libs",
+]
 
 [[package]]
 name = "memchr"

Cargo.toml

@@ -1,9 +1,10 @@
 [workspace]
 members = [
 	"template",
+	"aoc_libs",
 	"days/*",
 ]
-default-members = [ "days/*" ]
+default-members = [ "days/*", "aoc_libs" ]
 resolver = "2"
 
 [workspace.package]
@@ -13,6 +14,7 @@ edition = "2021"
 description = "advent of code 2022 in rust"
 
 [workspace.dependencies]
+aoc_libs = {path = "./aoc_libs"}
 regex = "1"
 once_cell = "1.16"
 thiserror = "1.0"

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
+    }
+}

days/day09/Cargo.toml

@@ -3,3 +3,7 @@ name = "day09"
 authors.workspace = true
 description.workspace = true
 version.workspace = true
+edition.workspace = true
+
+[dependencies]
+aoc_libs.workspace = true

days/day09/src/main.rs

@@ -10,8 +10,8 @@ fn main() {
     let structured_input = parse::parse(input);
 
     println!("Part One");
-    println!("Result: {}", part1::part1());
+    println!("Result: {}", part1::part1(&structured_input));
 
-    println!("Part Two");
-    println!("Result: {}", part2::part2());
+    // println!("Part Two");
+    // println!("Result: {}", part2::part2(&structured_input));
 }

days/day09/src/part1.rs

@@ -1,8 +1,19 @@
-//TODO:
-#![allow(unused)]
+use std::collections::HashSet;
 
-pub fn part1() -> usize {
-    unimplemented!()
+use aoc_libs::points::Point;
+
+use crate::parse::Direction;
+use crate::rope::Rope;
+
+pub fn part1(input: &Vec<Direction>) -> usize {
+    let mut visited: HashSet<Point> = HashSet::new();
+    let mut rope: Rope<2> = Rope::new();
+    visited.insert(*rope.get_tail_pos());
+    for direction in input {
+        rope.update_rope(direction);
+        visited.insert(*rope.get_tail_pos());
+    }
+    visited.len()
 }
 
 #[cfg(test)]
@@ -11,6 +22,32 @@ mod tests {
 
     #[test]
     fn test_part1() {
-        assert_eq!(0, 0);
+        let input = vec![
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Up,
+            Direction::Up,
+            Direction::Up,
+            Direction::Up,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Down,
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Down,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Right,
+            Direction::Right,
+        ];
+        assert_eq!(part1(&input), 13);
     }
 }

days/day09/src/part2.rs

@@ -1,8 +1,18 @@
-//TODO:
-#![allow(unused)]
+use std::collections::HashSet;
 
-pub fn part2() -> usize {
-    unimplemented!()
+use aoc_libs::points::Point;
+
+use crate::{rope::Rope, parse::Direction};
+
+pub fn part2(input: &Vec<Direction>) -> usize {
+    let mut visited: HashSet<Point> = HashSet::new();
+    let mut rope: Rope<10> = Rope::new();
+    for direction in input {
+        visited.insert(*rope.get_tail_pos());
+        rope.update_rope(direction);
+        println!("{}", rope)
+    }
+    visited.len()
 }
 
 #[cfg(test)]

days/day09/src/rope.rs

@@ -1,53 +1,48 @@
+use std::fmt::Display;
+
 use crate::parse::Direction;
-#[derive(Debug, Clone, Copy)]
-struct Point {
-    x: isize,
-    y: isize,
-}
-
-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::Sub for Point {
-    type Output = Point;
-
-    fn sub(self, rhs: Self) -> Self::Output {
-        Self {
-            x: self.x - rhs.x,
-            y: self.y - rhs.y,
-        }
-    }
-}
+use aoc_libs::points::{Point, UPoint};
 
 // L is the length of the rope in segments.
 #[derive(Debug)]
-struct Rope<const L: usize> {
+pub struct Rope<const L: usize> {
     segments: [Point; L],
 }
 
 impl<const L: usize> Rope<L> {
-    pub fn new()->Rope{
-        Rope { segments: () }
+    pub fn new() -> Rope<L> {
+        Rope {
+            segments: [Point::default(); L],
+        }
     }
 
-    pub fn update_rope(&mut self, direction: Direction) {
-        todo!()
+    pub fn update_rope(&mut self, direction: &Direction) {
+        self.segments[0] += match direction {
+            Direction::Up => Point { x: 0, y: 1 },
+            Direction::Right => Point { x: 1, y: 0 },
+            Direction::Down => Point { x: 0, y: -1 },
+            Direction::Left => Point { x: -1, y: 0 },
+        };
+        println!("direction is {:?}", direction);
+        for segment in 1..self.segments.len() {
+            self.segments[segment] += Rope::<L>::update_single_segment_pair(
+                &self.segments[segment - 1],
+                &self.segments[segment],
+            )
+        }
+        println!("{}", self);
     }
 
     pub fn get_tail_pos(&self) -> &Point {
         &self.segments[self.segments.len() - 1]
     }
 
-    fn update_single_segment_pair(head: Point, tail: Point) -> Point {
-        let delta = head - tail;
+    // the rope segment will not move if the segment ahead of it is only at most one away, and will
+    // move with the following rules if it is 2 away: It moves straight towards the head if the
+    // head is directly up/down/left/right, and diagonally towards it if its not straight
+    // up/down/left/right.
+    fn update_single_segment_pair(head: &Point, tail: &Point) -> Point {
+        let delta = *head - *tail;
         if delta.x.abs() > 2 || delta.y.abs() > 2 {
             panic!("invalid delta ({}, {})", delta.y, delta.x)
         }
@@ -64,3 +59,102 @@ impl<const L: usize> Rope<L> {
         }
     }
 }
+
+impl<const L: usize> Display for Rope<{ L }> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let grid_size = (self.segments.len() * 2) - 1;
+        let zero_point = UPoint {
+            x: self.segments.len() - 1,
+            y: self.segments.len() - 1,
+        };
+
+        let mut grid: Vec<Vec<char>> = Vec::with_capacity(grid_size);
+        for y in 0..grid_size {
+            grid.push(Vec::with_capacity(grid_size));
+            for _ in 0..grid_size {
+                grid[y].push('.')
+            }
+        }
+
+        for segment in self.segments.iter().skip(1) {
+            let delta =  *segment-self.segments[0];
+            let upoint = delta.to_upoint(&zero_point).unwrap();
+            grid[upoint.y][upoint.x] = 'T'
+        }
+
+        writeln!(
+            f,
+            "head is at {}, {}",
+            self.segments[0].x, self.segments[0].y
+        )?;
+        let upoint = Point { x: 0, y: 0 }.to_upoint(&zero_point).unwrap();
+        grid[upoint.y][upoint.x] = 'H';
+
+        for line in grid {
+            let mut writeline = "".to_string();
+            for char in line {
+                writeline.push(char)
+            }
+            writeln!(f, "{}", writeline)?;
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashSet;
+
+    use super::*;
+
+    #[test]
+    fn test_single_segment() {
+        let input = [
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Up,
+            Direction::Up,
+            Direction::Up,
+            Direction::Up,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Down,
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Right,
+            Direction::Down,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Left,
+            Direction::Right,
+            Direction::Right,
+        ];
+        let mut visited: HashSet<Point> = HashSet::new();
+        let mut rope: Rope<2> = Rope::new();
+        visited.insert(*rope.get_tail_pos());
+        for direction in input {
+            rope.update_rope(&direction);
+            visited.insert(*rope.get_tail_pos());
+        }
+        // let mut graph = [
+        //     ['.', '.', '.', '.', '.', '.'],
+        //     ['.', '.', '.', '.', '.', '.'],
+        //     ['.', '.', '.', '.', '.', '.'],
+        //     ['.', '.', '.', '.', '.', '.'],
+        //     ['s', '.', '.', '.', '.', '.'],
+        // ];
+        // for point in &visited {
+        //     graph[4 - point.y as usize][point.x as usize] = '#';
+        // }
+        // for line in graph {
+        //     println!("{:?}", line)
+        // }
+        assert_eq!(visited.len(), 13)
+    }
+}

template/Cargo.toml

@@ -3,3 +3,4 @@ name = "template"
 authors.workspace = true
 description.workspace = true
 version.workspace = true
+edition.workspace = true