feat: upload day 6

Author: Nitestack

2024/day-6/Cargo.lock

@@ -0,0 +1,7 @@
+[package]
+name = "day-6"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+glam = "0.29.2"

2024/day-6/Cargo.toml

@@ -0,0 +1,115 @@
+// ╭─────────────────────────────────────────────────────────╮
+// │ Advent of Code 2024 - Day 6                             │
+// ╰─────────────────────────────────────────────────────────╯
+
+use std::collections::HashSet;
+
+use glam::{ ivec2, IVec2 };
+
+const LEFT: IVec2 = ivec2(-1, 0);
+const RIGHT: IVec2 = ivec2(1, 0);
+const UP: IVec2 = ivec2(0, -1);
+const DOWN: IVec2 = ivec2(0, 1);
+
+#[derive(PartialEq, Clone)]
+enum Tile {
+    Empty,
+    Obstruction
+}
+
+#[derive(PartialEq, Eq, Hash, Clone, Copy)]
+enum Direction {
+    Left,
+    Right,
+    Up,
+    Down
+}
+impl Direction {
+    fn vec(&self) -> IVec2 {
+        match self {
+            Direction::Left => LEFT,
+            Direction::Right => RIGHT,
+            Direction::Up => UP,
+            Direction::Down => DOWN
+        }
+    }
+    fn rotate_right(&self) -> Self {
+        match self {
+            Direction::Left => Direction::Up,
+            Direction::Right => Direction::Down,
+            Direction::Up => Direction::Right,
+            Direction::Down => Direction::Left,
+        }
+    }
+}
+
+struct Guard {
+    pos: IVec2,
+    initial_pos: IVec2,
+    direction: Direction,
+}
+impl Guard {
+    fn new(pos: IVec2) -> Self {
+        Guard { pos, initial_pos: pos, direction: Direction::Up }
+    }
+    fn reset(&mut self) -> &Self {
+        self.pos = self.initial_pos;
+        self.direction = Direction::Up;
+        self
+    }
+}
+
+fn main() {
+    let input = include_str!("../input.txt");
+
+    let mut guard = Guard::new(ivec2(0, 0));
+
+    let map = input
+        .lines()
+        .enumerate()
+        .map(|(y, line)| line.chars().enumerate().map(|(x, tile)| match tile {
+            '^' => {
+                guard = Guard::new(ivec2(x as i32, y as i32));
+                Tile::Empty
+            },
+            '#' => Tile::Obstruction,
+            '.' => Tile::Empty,
+            _ => panic!("Invalid input")
+        }).collect::<Vec<_>>()).collect::<Vec<_>>();
+    let mut positions = HashSet::from([guard.initial_pos]);
+    // ── Part 1 ──────────────────────────────────────────────────────────
+    loop {
+        let next_pos = guard.pos + guard.direction.vec();
+        if next_pos.x < 0 || next_pos.y < 0 || next_pos.x >= map[0].len() as i32 || next_pos.y >= map.len() as i32 { break; }
+        if map[next_pos.y as usize][next_pos.x as usize] == Tile::Obstruction {
+            guard.direction = guard.direction.rotate_right();
+            continue;
+        }
+        guard.pos = next_pos;
+        positions.insert(next_pos);
+    }
+    println!("Number of positions visited: {}", positions.len());
+    // ── Part 2 ──────────────────────────────────────────────────────────
+    let mut obstruction_positions: usize = 0;
+    for pos in positions {
+        guard.reset();
+        let mut new_map = map.clone();
+        new_map[pos.y as usize][pos.x as usize] = Tile::Obstruction;
+
+        let mut new_positions = HashSet::new();
+        loop {
+            if !new_positions.insert((guard.pos, guard.direction)) {
+                obstruction_positions += 1;
+                break;
+            }
+            let next_pos = guard.pos + guard.direction.vec();
+            if next_pos.x < 0 || next_pos.y < 0 || next_pos.x >= map[0].len() as i32 || next_pos.y >= map.len() as i32 { break; }
+            if new_map[next_pos.y as usize][next_pos.x as usize] == Tile::Obstruction {
+                guard.direction = guard.direction.rotate_right();
+                continue;
+            }
+            guard.pos = next_pos;
+        }
+    }
+    println!("Different obstruction positions: {obstruction_positions}");
+}