day15 - cleanup

day15.py

@@ -1,4 +1,5 @@
 from collections import deque
+from enum import Enum
 from tools.aoc import AOCDay
 from tools.coordinate import Coordinate
 from tools.grid import Grid
@@ -20,71 +21,57 @@ LARGER = {
 }
 
 
+class Tile(str, Enum):
+    EMPTY = "."
+    WALL = "#"
+    BOX = "O"
+    BOX_LEFT = "["
+    BOX_RIGHT = "]"
+
+
 def sokoban(grid: Grid, start: Coordinate, moves: str) -> Grid:
     for move in moves:
         dir_ = MOVES[move]
         next_pos = start + dir_
-        if grid.get(next_pos) == ".":
-            start += dir_
+        if grid.get(next_pos) == Tile.WALL:
             continue
-        elif grid.get(next_pos) == "#":
-            continue
-        elif grid.get(next_pos) == "O":
-            pos_behind_box = next_pos + dir_
-            while grid.get(pos_behind_box) == "O":
-                pos_behind_box += dir_
-
-            if grid.get(pos_behind_box) == "#":
-                continue
-
-            grid.set(pos_behind_box, "O")
+        elif grid.get(next_pos) == Tile.EMPTY:
             start = next_pos
-            grid.set(start, ".")
             continue
 
-        if move in ["<", ">"]:
-            # easy mode
-            pos_behind_box = next_pos + dir_
-            while grid.get(pos_behind_box) in ["[", "]"]:
-                pos_behind_box += dir_ * 2
-
-            if grid.get(pos_behind_box) == "#":
+        # neither a wall, nor empty space? There must be a box in the way
+        to_move = set()
+        wall_in_the_way = False
+        queue = deque([next_pos])
+        while queue:
+            pos = queue.popleft()
+            pos_tile = grid.get(pos)
+            if pos_tile == Tile.EMPTY:
                 continue
 
-            while pos_behind_box != start:
-                grid.set(pos_behind_box, grid.get(pos_behind_box - dir_))
-                pos_behind_box -= dir_
-        else:
-            # recursive mode
-            wall_in_the_way = False
-            Q = deque([next_pos])
-            boxes = set()
-            while Q:
-                pos = Q.popleft()
-                if grid.get(pos) == "#":
-                    wall_in_the_way = True
-                    break
-                elif grid.get(pos) == ".":
-                    continue
+            if pos_tile == Tile.WALL:
+                wall_in_the_way = True
+                break
 
-                Q.append(pos + dir_)
-                if grid.get(pos) == "[":
-                    boxes.add((pos, pos + (1, 0)))
-                    Q.append(pos + dir_ + (1, 0))
+            if (pos, pos_tile) in to_move:
+                continue
+
+            to_move.add((pos, pos_tile))
+            queue.append(pos + dir_)
+            if pos_tile in [Tile.BOX_LEFT, Tile.BOX_RIGHT]:
+                if pos_tile == Tile.BOX_LEFT:
+                    queue.append(pos + (1, 0))
                 else:
-                    boxes.add((pos + (-1, 0), pos))
-                    Q.append(pos + dir_ + (-1, 0))
+                    queue.append(pos + (-1, 0))
 
-            if wall_in_the_way:
-                continue
+        if wall_in_the_way:
+            continue
 
-            for box_l, box_r in boxes:
-                grid.set(box_l, ".")
-                grid.set(box_r, ".")
+        for box, _ in to_move:
+            grid.set(box, Tile.EMPTY)
 
-            for box_l, box_r in boxes:
-                grid.set(box_l + dir_, "[")
-                grid.set(box_r + dir_, "]")
+        for box, box_tile in to_move:
+            grid.set(box + dir_, box_tile)
 
         start = next_pos
 
@@ -108,7 +95,7 @@ class Day(AOCDay):
         map_, moves = self.getMultiLineInputAsArray()
         if part2:
             map_ = ["".join([LARGER[x] for x in y]) for y in map_]
-        grid = Grid.from_data(map_, default=".")
+        grid = Grid.from_data(map_, default=Tile.EMPTY, translate={r"\.#O\[\]": Tile})
         start = list(grid.find("@"))[0]
         grid.set(start, ".")