Day 22: Monkey Map

README.md

@@ -27,4 +27,4 @@ Development occurs in language-specific directories:
 |[Day19.hs](hs/src/Day19.hs)|[Day19.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day19.kt)|[day19.py](py/aoc2022/day19.py)|[day19.rs](rs/src/day19.rs)|
 |[Day20.hs](hs/src/Day20.hs)|[Day20.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day20.kt)|[day20.py](py/aoc2022/day20.py)|[day20.rs](rs/src/day20.rs)|
 |[Day21.hs](hs/src/Day21.hs)|[Day21.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day21.kt)|[day21.py](py/aoc2022/day21.py)|[day21.rs](rs/src/day21.rs)|
-|[Day22.hs](hs/src/Day22.hs)|[Day22.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day22.kt)|
+|[Day22.hs](hs/src/Day22.hs)|[Day22.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day22.kt)|[day22.py](py/aoc2022/day22.py)|

py/aoc2022/day22.py

@@ -0,0 +1,163 @@
+"""
+Day 22: Monkey Map
+"""
+
+import itertools
+import math
+import operator
+import re
+
+SAMPLE_INPUT = [
+    "        ...#",
+    "        .#..",
+    "        #...",
+    "        ....",
+    "...#.......#",
+    "........#...",
+    "..#....#....",
+    "..........#.",
+    "        ...#....",
+    "        .....#..",
+    "        .#......",
+    "        ......#.",
+    "",
+    "10R5L5R10L4R5L5",
+]
+
+PATTERN = re.compile(r"(\d+)|([LR])")
+
+
+def _parse(lines):
+    lines = iter(lines)
+    board = [""]
+    for line in lines:
+        line = line.rstrip()
+        if not line:
+            break
+        board.append(f" {line} ")
+    board.append("")
+    max_len = max(len(line) for line in board)
+    for i, line in enumerate(board):
+        board[i] = line.ljust(max_len, " ")
+    moves = [
+        int(match.group(1)) if match.group(1) else match.group(2)
+        for match in re.finditer(PATTERN, next(lines))
+    ]
+    return board, moves
+
+
+def _perimeter(board: list[str]):
+    initial_x = board[1].index(".")
+    x, y, direction = initial_x, 1, 0
+    while True:
+        yield x, y, direction
+        forward_x = (x + 1, x, x - 1, x)[direction]
+        forward_y = (y, y + 1, y, y - 1)[direction]
+        if board[forward_y][forward_x] == " ":
+            direction = (direction + 1) % 4
+        else:
+            left_x = (x + 1, x + 1, x - 1, x - 1)[direction]
+            left_y = (y - 1, y + 1, y + 1, y - 1)[direction]
+            if board[left_y][left_x] == " ":
+                x, y = forward_x, forward_y
+            else:
+                x, y, direction = left_x, left_y, (direction - 1) % 4
+        if x == initial_x and y == 1 and direction == 0:
+            break
+
+
+def _run(board, moves, warps):
+    x, y, direction = board[1].index("."), 1, 0
+    for move in moves:
+        match move:
+            case "L":
+                direction = (direction - 1) % 4
+            case "R":
+                direction = (direction + 1) % 4
+            case _:
+                for _ in range(move):
+                    next_x, next_y, next_direction = (
+                        warps[x, y, direction]
+                        if (x, y, direction) in warps
+                        else (
+                            (x + 1, x, x - 1, x)[direction],
+                            (y, y + 1, y, y - 1)[direction],
+                            direction,
+                        )
+                    )
+                    if board[next_y][next_x] != ".":
+                        break
+                    x, y, direction = next_x, next_y, next_direction
+    return 1000 * y + 4 * x + direction
+
+
+def part1(lines):
+    """
+    >>> part1(SAMPLE_INPUT)
+    6032
+    """
+    board, moves = _parse(lines)
+    warps = {}
+    for x, y, direction in _perimeter(board):
+        warp_x, warp_y, direction = x, y, (direction - 1) % 4
+        if direction == 0:
+            warp_x = next(x for x in range(len(board[y])) if board[y][x] != " ")
+        elif direction == 1:
+            warp_y = next(y for y in range(len(board)) if board[y][x] != " ")
+        elif direction == 2:
+            warp_x = next(
+                x for x in range(len(board[y]) - 1, -1, -1) if board[y][x] != " "
+            )
+        elif direction == 3:
+            warp_y = next(
+                y for y in range(len(board) - 1, -1, -1) if board[y][x] != " "
+            )
+        warps[x, y, direction] = warp_x, warp_y, direction
+    return _run(board, moves, warps)
+
+
+def part2(lines):
+    # pylint: disable=too-many-locals
+    """
+    >>> part2(SAMPLE_INPUT)
+    5031
+    """
+    board, moves = _parse(lines)
+    edges = [
+        (key, list(edge))
+        for key, edge in itertools.groupby(_perimeter(board), operator.itemgetter(2))
+    ]
+    side_length = math.gcd(*(len(edge) for _, edge in edges))
+    edges = [
+        (direction, edge[i : i + side_length])
+        for direction, edge in edges
+        for i in range(0, len(edge), side_length)
+    ]
+    pairs = []
+    while edges:
+        i = 0
+        while i < len(edges) - 1:
+            direction1, edge1 = edges[i]
+            direction2, edge2 = edges[i + 1]
+            if (direction1 - direction2) % 4 == 1:
+                pairs.append((edge1, edge2))
+                edges[i : i + 2] = []
+                edges[i:] = (
+                    ((direction - 1) % 4, edge) for direction, edge in edges[i:]
+                )
+            else:
+                i += 1
+    warps = {}
+    for edge1, edge2 in pairs:
+        for point1, point2 in zip(edge1, edge2[::-1]):
+            x1, y1, direction1 = point1
+            x2, y2, direction2 = point2
+            warps[x1, y1, (direction1 - 1) % 4] = x2, y2, (direction2 + 1) % 4
+            warps[x2, y2, (direction2 - 1) % 4] = x1, y1, (direction1 + 1) % 4
+    return _run(board, moves, warps)
+
+
+parts = (part1, part2)
+
+if __name__ == "__main__":
+    print(part1(SAMPLE_INPUT))

py/pyproject.toml

@@ -53,6 +53,7 @@ day18 = "aoc2022.day18:parts"
 day19 = "aoc2022.day19:parts"
 day20 = "aoc2022.day20:parts"
 day21 = "aoc2022.day21:parts"
+day22 = "aoc2022.day22:parts"
 
 [tool.black]
 target_version = ["py311"]