2022 day9/rust: add solution

2022/data/day9.expected

@@ -0,0 +1,2 @@
+5619
+2376

2022/day9/rust/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "rust_2022_09"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aoc = { path = "../../../common/rust" }

2022/day9/rust/src/main.rs

@@ -0,0 +1,115 @@
+#![warn(clippy::pedantic)]
+
+use std::{
+    collections::BTreeSet,
+    io::{stdin, Read},
+    ops::{Add, AddAssign, Sub},
+};
+
+use aoc::*;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Vec2 {
+    x: i32, // increases toward right
+    y: i32, // increases toward top
+}
+
+impl Vec2 {
+    #[must_use]
+    pub fn new(x: i32, y: i32) -> Self {
+        Self { x, y }
+    }
+
+    #[must_use]
+    pub fn map(self, mut f: impl FnMut(i32) -> i32) -> Self {
+        Self {
+            x: f(self.x),
+            y: f(self.y),
+        }
+    }
+}
+
+impl Add for Vec2 {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Self {
+            x: self.x + rhs.x,
+            y: self.y + rhs.y,
+        }
+    }
+}
+
+impl AddAssign for Vec2 {
+    fn add_assign(&mut self, rhs: Self) {
+        self.x += rhs.x;
+        self.y += rhs.y;
+    }
+}
+
+impl Sub for Vec2 {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Self {
+            x: self.x - rhs.x,
+            y: self.y - rhs.y,
+        }
+    }
+}
+
+impl From<(i32, i32)> for Vec2 {
+    fn from((x, y): (i32, i32)) -> Self {
+        Self { x, y }
+    }
+}
+
+impl From<Vec2> for (i32, i32) {
+    fn from(v: Vec2) -> Self {
+        (v.x, v.y)
+    }
+}
+
+fn get_direction_vec(direction: &str) -> Vec2 {
+    match direction {
+        "U" => (0, 1),
+        "R" => (1, 0),
+        "D" => (0, -1),
+        "L" => (-1, 0),
+        _ => panic!(),
+    }
+    .into()
+}
+
+fn main() {
+    let mut data = String::new();
+    stdin().read_to_string(&mut data).unwrap();
+
+    let mut knots = vec![Vec2::new(0, 0); 10];
+
+    let mut tail_positions = BTreeSet::new();
+    tail_positions.insert(*knots.last().unwrap());
+
+    for line in data.lines() {
+        let (direction, distance) = line.split_once(' ').unwrap();
+        let distance: usize = distance.parse().unwrap();
+
+        for _i in 0..distance {
+            knots[0] += get_direction_vec(direction);
+            let mut following = knots[0];
+
+            for knot in &mut knots[1..] {
+                let delta = match (following - *knot).into() {
+                    (x, y) if x.abs() <= 1 && y.abs() <= 1 => (0, 0),
+                    (x, y) => (x.signum(), y.signum()),
+                }
+                .into();
+                *knot += delta;
+                following = *knot;
+            }
+            tail_positions.insert(*knots.last().unwrap());
+        }
+    }
+
+    println!("{:?}", tail_positions.len());
+}

Cargo.lock

@@ -524,6 +524,13 @@ dependencies = [
  "aoc",
 ]
 
+[[package]]
+name = "rust_2022_09"
+version = "0.1.0"
+dependencies = [
+ "aoc",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.11"

Cargo.toml

@@ -18,4 +18,5 @@ members = [
 	"2022/day6/rust",
 	"2022/day7/rust",
 	"2022/day8/rust",
+	"2022/day9/rust",
 ]