Add day15 part2

day15/src/main.rs

@@ -2,11 +2,13 @@ use std::{collections::VecDeque, fmt::Display};
 
 use glam::IVec2;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Copy)]
 enum Tile {
     Wall,
     Robot,
     Box,
+    BoxL,
+    BoxR,
     Empty,
 }
 use Tile::*;
@@ -17,6 +19,8 @@ impl Display for Tile {
             Wall => write!(f, "#"),
             Robot => write!(f, "@"),
             Box => write!(f, "O"),
+            BoxL => write!(f, "["),
+            BoxR => write!(f, "]"),
             Empty => write!(f, "."),
         }
     }
@@ -62,6 +66,27 @@ impl Display for State {
     }
 }
 
+impl State {
+    fn widen(&mut self) {
+        self.map = self
+            .map
+            .iter()
+            .map(|l| {
+                l.iter()
+                    .flat_map(|t| match t {
+                        Empty => [Empty, Empty],
+                        Wall => [Wall, Wall],
+                        Box => [BoxL, BoxR],
+                        Robot => [Robot, Empty],
+                        e => [*e, *e],
+                    })
+                    .collect()
+            })
+            .collect();
+        self.robot_pos *= IVec2::new(1, 2);
+    }
+}
+
 fn parse(input: &str) -> State {
     let (map, directions) = input.split_once("\n\n").unwrap();
     let mut robot_pos = IVec2::new(0, 0);
@@ -105,6 +130,31 @@ 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 can_be_moved(state: &State, pos: &IVec2, direction: &IVec2, to_move: &mut Vec<IVec2>) -> bool {
+    let tile_in_front = state.map[(pos + direction).x as usize][(pos + direction).y as usize];
+    if tile_in_front == Wall {
+        return false;
+    }
+    if tile_in_front == Empty {
+        return true;
+    }
+
+    let to_check_dir = match tile_in_front {
+        BoxL => Right.as_vec(),
+        BoxR => Left.as_vec(),
+        _ => IVec2::new(0, 0),
+    };
+
+    if direction == &Up.as_vec() || direction == &Down.as_vec() {
+        to_move.push(pos + direction);
+        to_move.push(pos + direction + to_check_dir);
+        return can_be_moved(state, &(pos + direction), direction, to_move)
+            && can_be_moved(state, &(pos + direction + to_check_dir), direction, to_move);
+    }
+    to_move.push(pos + direction);
+    can_be_moved(state, &(pos + direction), direction, to_move)
+}
+
 fn do_move(state: &mut State) {
     let dir = state.directions.pop_front().unwrap().as_vec();
     let pos_in_front = state.robot_pos + dir;
@@ -120,42 +170,50 @@ fn do_move(state: &mut State) {
         return;
     }
 
-    let mut curr = pos_in_front;
-    while get_tile(&mut state.map, &curr) != &Wall && get_tile(&mut state.map, &curr) != &Empty {
-        curr += dir;
+    let mut to_move = Vec::new();
+    if can_be_moved(state, &state.robot_pos, &dir, &mut to_move) {
+        let mut new_map = state.map.clone();
+        for pos in &to_move {
+            *get_tile(&mut new_map, pos) = Empty;
+        }
+
+        for pos in &to_move {
+            *get_tile(&mut new_map, &(pos + dir)) = *get_tile(&mut state.map, pos);
+        }
+        state.map = new_map;
+        *get_tile(&mut state.map, &pos_in_front) = Robot;
+        *get_tile(&mut state.map, &state.robot_pos) = Empty;
+        state.robot_pos = pos_in_front;
     }
-    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);
-    }
+fn get_gps_sum(state: &State) -> usize {
     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
-                    }
-                },
-            )
+            l.iter().enumerate().map(move |(t_idx, t)| {
+                if t == &Box || t == &BoxL {
+                    100 * l_idx + t_idx
+                } else {
+                    0
+                }
+            })
         })
         .sum()
 }
 
+fn part12(state: &mut State) -> usize {
+    while !state.directions.is_empty() {
+        do_move(state);
+    }
+    get_gps_sum(state)
+}
+
 fn main() {
     let mut input = parse(include_str!("../input.txt"));
-    println!("{}", part1(&mut input));
+    println!("{}", part12(&mut input.clone()));
+    input.widen();
+    println!("{}", part12(&mut input));
 }