From b813526dfe07121238ca8b9095695bff36f616b3 Mon Sep 17 00:00:00 2001
From: Adrian Groh <adrian.groh@t-online.de>
Date: Sun, 15 Dec 2024 09:55:29 +0100
Subject: [PATCH] Add day15 part 1

---
 day15/Cargo.lock  |  16 +++++
 day15/Cargo.toml  |   7 ++
 day15/src/main.rs | 161 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 184 insertions(+)
 create mode 100644 day15/Cargo.lock
 create mode 100644 day15/Cargo.toml
 create mode 100644 day15/src/main.rs

diff --git a/day15/Cargo.lock b/day15/Cargo.lock
new file mode 100644
index 0000000..5f78868
--- /dev/null
+++ b/day15/Cargo.lock
@@ -0,0 +1,16 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day15"
+version = "0.1.0"
+dependencies = [
+ "glam",
+]
+
+[[package]]
+name = "glam"
+version = "0.29.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc46dd3ec48fdd8e693a98d2b8bafae273a2d54c1de02a2a7e3d57d501f39677"
diff --git a/day15/Cargo.toml b/day15/Cargo.toml
new file mode 100644
index 0000000..9d9b5b7
--- /dev/null
+++ b/day15/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "day15"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+glam = "0.29.2"
diff --git a/day15/src/main.rs b/day15/src/main.rs
new file mode 100644
index 0000000..e5d635f
--- /dev/null
+++ b/day15/src/main.rs
@@ -0,0 +1,161 @@
+use std::{collections::VecDeque, fmt::Display};
+
+use glam::IVec2;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum Tile {
+    Wall,
+    Robot,
+    Box,
+    Empty,
+}
+use Tile::*;
+
+impl Display for Tile {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Wall => write!(f, "#"),
+            Robot => write!(f, "@"),
+            Box => write!(f, "O"),
+            Empty => write!(f, "."),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+use Direction::*;
+
+impl Direction {
+    fn as_vec(&self) -> IVec2 {
+        match self {
+            Up => IVec2::new(-1, 0),
+            Down => IVec2::new(1, 0),
+            Left => IVec2::new(0, -1),
+            Right => IVec2::new(0, 1),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+struct State {
+    map: Vec<Vec<Tile>>,
+    directions: VecDeque<Direction>,
+    robot_pos: IVec2,
+}
+
+impl Display for State {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{}",
+            self.map
+                .iter()
+                .map(|l| l.iter().map(|t| t.to_string()).collect::<String>() + "\n")
+                .collect::<String>()
+        )
+    }
+}
+
+fn parse(input: &str) -> State {
+    let (map, directions) = input.split_once("\n\n").unwrap();
+    let mut robot_pos = IVec2::new(0, 0);
+    State {
+        map: map
+            .lines()
+            .enumerate()
+            .map(|(l_idx, l)| {
+                l.chars()
+                    .enumerate()
+                    .map(|(c_idx, c)| match c {
+                        '#' => Wall,
+                        '@' => {
+                            robot_pos.x = l_idx as i32;
+                            robot_pos.y = c_idx as i32;
+                            Robot
+                        }
+                        'O' => Box,
+                        _ => Empty,
+                    })
+                    .collect()
+            })
+            .collect(),
+        directions: directions
+            .replace("\n", "")
+            .chars()
+            .map(|c| match c {
+                '<' => Left,
+                '^' => Up,
+                '>' => Right,
+                'v' => Down,
+                _ => panic!(),
+            })
+            .collect(),
+        robot_pos,
+    }
+}
+
+#[inline]
+fn get_tile<'a>(map: &'a mut [Vec<Tile>], idx: &IVec2) -> &'a mut Tile {
+    &mut map[idx.x as usize][idx.y as usize]
+}
+
+fn do_move(state: &mut State) {
+    let dir = state.directions.pop_front().unwrap().as_vec();
+    let pos_in_front = state.robot_pos + dir;
+
+    if get_tile(&mut state.map, &pos_in_front) == &Wall {
+        return;
+    }
+
+    if get_tile(&mut state.map, &pos_in_front) == &Empty {
+        *get_tile(&mut state.map, &pos_in_front) = Robot;
+        *get_tile(&mut state.map, &state.robot_pos) = Empty;
+        state.robot_pos = pos_in_front;
+        return;
+    }
+
+    let mut curr = pos_in_front;
+    while get_tile(&mut state.map, &curr) != &Wall && get_tile(&mut state.map, &curr) != &Empty {
+        curr += dir;
+    }
+    if get_tile(&mut state.map, &curr) == &Wall {
+        return;
+    }
+    *get_tile(&mut state.map, &curr) = Box;
+    *get_tile(&mut state.map, &pos_in_front) = Robot;
+    *get_tile(&mut state.map, &state.robot_pos) = Empty;
+    state.robot_pos = pos_in_front;
+}
+
+fn part1(state: &mut State) -> usize {
+    while !state.directions.is_empty() {
+        do_move(state);
+    }
+    state
+        .map
+        .iter()
+        .enumerate()
+        .flat_map(|(l_idx, l)| {
+            l.iter().enumerate().map(
+                move |(t_idx, t)| {
+                    if t == &Box {
+                        100 * l_idx + t_idx
+                    } else {
+                        0
+                    }
+                },
+            )
+        })
+        .sum()
+}
+
+fn main() {
+    let mut input = parse(include_str!("../input.txt"));
+    println!("{}", part1(&mut input));
+}