Day 24.

2022/day24.py

@@ -1,3 +1,104 @@
 # -*- encoding: utf-8 -*-
 
+import heapq
+import math
 import sys
+from collections import defaultdict
+
+lines = sys.stdin.read().splitlines()
+
+winds = {
+    (i - 1, j - 1, lines[i][j])
+    for i in range(1, len(lines) - 1)
+    for j in range(1, len(lines[i]) - 1)
+    if lines[i][j] != "."
+}
+
+n_rows, n_cols = len(lines) - 2, len(lines[0]) - 2
+CYCLE = math.lcm(n_rows, n_cols)
+
+# for each row, set of forward winds
+east_winds = [{j for j in range(n_cols) if (i, j, ">") in winds} for i in range(n_rows)]
+west_winds = [{j for j in range(n_cols) if (i, j, "<") in winds} for i in range(n_rows)]
+north_winds = [
+    {i for i in range(n_rows) if (i, j, "^") in winds} for j in range(n_cols)
+]
+south_winds = [
+    {i for i in range(n_rows) if (i, j, "v") in winds} for j in range(n_cols)
+]
+
+
+def run(start: tuple[int, int], start_cycle: int, end: tuple[int, int]):
+    def heuristic(y: int, x: int) -> int:
+        return abs(end[0] - y) + abs(end[1] - x)
+
+    # (distance + heuristic, distance, start_pos)
+    queue = [(heuristic(start[0], start[1]), 0, ((start[0], start[1]), start_cycle))]
+    visited: set[tuple[tuple[int, int], int]] = set()
+    distances: dict[tuple[int, int], dict[int, int]] = defaultdict(lambda: {})
+
+    while queue:
+        _, distance, ((y, x), cycle) = heapq.heappop(queue)
+        # print(y, x, distance, cycle)
+
+        if ((y, x), cycle) in visited:
+            continue
+
+        distances[y, x][cycle] = distance
+
+        visited.add(((y, x), cycle))
+
+        if (y, x) == (end[0], end[1]):
+            break
+
+        for dy, dx in (0, 0), (-1, 0), (1, 0), (0, -1), (0, 1):
+            ty = y + dy
+            tx = x + dx
+
+            n_cycle = (cycle + 1) % CYCLE
+
+            if (ty, tx) == end:
+                heapq.heappush(queue, (distance + 1, distance + 1, ((ty, tx), n_cycle)))
+                break
+
+            if ((ty, tx), n_cycle) in visited:
+                continue
+
+            if (ty, tx) != start and (ty < 0 or tx < 0 or ty >= n_rows or tx >= n_cols):
+                continue
+
+            if (ty, tx) != start:
+                if any(ty == (vy + n_cycle) % n_rows for vy in south_winds[tx]):
+                    continue
+                if any(ty == (vy - n_cycle) % n_rows for vy in north_winds[tx]):
+                    continue
+                if any(tx == (vx - n_cycle) % n_cols for vx in west_winds[ty]):
+                    continue
+                if any(tx == (vx + n_cycle) % n_cols for vx in east_winds[ty]):
+                    continue
+
+            # print(f"{y} {x} [{cycle}] -> {ty} {tx}")
+
+            heapq.heappush(
+                queue,
+                ((heuristic(ty, tx) + distance + 1, distance + 1, ((ty, tx), n_cycle))),
+            )
+
+    return distances, next(iter(distances[end].values()))
+
+
+start = (
+    -1,
+    next(j for j in range(1, len(lines[0]) - 1) if lines[0][j] == ".") - 1,
+)
+end = (
+    n_rows,
+    next(j for j in range(1, len(lines[-1]) - 1) if lines[-1][j] == ".") - 1,
+)
+
+distances_1, forward_1 = run(start, 0, end)
+print(f"answer 1 is {forward_1}")
+
+distances_2, return_1 = run(end, next(iter(distances_1[end].keys())), start)
+distances_3, forward_2 = run(start, next(iter(distances_2[start].keys())), end)
+print(f"answer 2 is {forward_1 + return_1 + forward_2}")

2022/inputs/day24.txt

@@ -0,0 +1,22 @@
+#.######################################################################################################################################################
+#.v><><<>^^^<><<>.^v<>v^>v^v^^<..^v>^>^vv.>v^<<>^.v<vvv<.>><v>><^>><>^<><v<>>>><v>v<^<>^.v..v^vv<v<<vv.v>>v<>v.<..^<vv<^v^v.v>>v>><^v>^<.vv^^<<><<>v>><#
+#.vv<vv<>.v<<<<<>>vv<>^v^^<^<>><.<^>^<^>^<v<<<<v>v>><.><.^><>vv<^^><<<<>^<.<v^.vv^vv>v>^.<<<><v<.v.<><<v^^v>^^<^>>^.<v^v.v><<v^vv<<v>^v>><^^<^<v>^>><v<#
+#<v^>v^vv<><v><<^<>^<^vv>v>>^^><<<vv><v.v.^><<^><>v>^<^v<<^>v<vv><v<<^.vv^>>>.^v>v.><v>v<^<^^<><<>><<^^^>v<^>>^v>>vv.<>^<><<^v>><^.>v^v><<^^^^<v<>^v<v.#
+#<<^<vv^<^><>^><>^vv.v^v>><^^<>^<>>^><^.^^<.v...>^^.^<<v<vvv>>>v^..^v.v<^><>.>v^.vv<^^vv>vv^.^.vv<v>>^>v.^^^<v<>><vv^>>^^.v>.v^^<^>vvv^<<v^<v<^><^>v<>>#
+#<.<^>>^<v><^>^^.>>v^<v^vvv>>vv.v^<>^^>v<<vv^<>^v.<<<^>>>.^>vvv.^^^<^><<^><v>><^.^>vv^^vv.><<v<^<v^^^.>v>^>v.^^<<^^^>^><><<vv<.<>v>vv>><^^v>>vvv^<...<<#
+#><v.v>vv>^^^>>><v>^^v>^>>><vv^<^<^<<<>.<<.<.<..><><v.v^^.v..v^>>>^v><.^^><<>v^<^<>^>>.v^v.v.>v>^>>>v>>^>><^<.v.v<^<<<<<^^>^^^^>^^<v^>>v><>.<>v><>.>><>#
+#<><<.>^<>^^v<v>^><^>v^.>><vv^vv^<v<<>.>.>>.vv.v<.^<^<>>^><><^.v>>v^^v><>><<<vv<<>v><>^.>>^>v^^><^<v<<><vv^>>.<^<.^<^>vvv>^<.v<^<>.><.>>v<^>^v<<.^<v>^<#
+#<>.<v^>.^<<^v^.<<^>v^^vv<^><^<^>><v^^vvv<<vvvv>>^v><<>^>vvvvv^<<v^.>^<.<^>.^>^><v^<>>.<<^^vv>>>^>vv><vvv^v.>^vv><<<<>^v^^^.>.^>>^^v^v>v>vv^<<^vv^<>v<>#
+#<<>v>v>>v^^v><^<.vv<^>^^>.v^<.^^vv>.<>^<>v>^>vvv<vv^>v^><<<v>vv<..^v^v>v.v><^.<^>.v<v><v>v^>^<<<<<>^.v<^.<v.<<^>v^^^<^<<>v.<<^<<<<.<^><<<^<v<v>>v>.><>#
+#>>.>vvv<<..>^^vv^>.<.v..v^^>^v<<>>>vv.<v>vv^<vv^v><v^^.<<.><..><^><<>^<<><v<.<v.<^<^.^<^<<><><<^v^>.<<v^^>.^<...v.^<^^<><><>v^<><^>^>^v^.>^^>^.vv.<v^>#
+#>.<><v>v<v>v>^v^^v>.v^.v>v>.<>>>^vv<<v>>^>^.^<^vv.vvvv<<>v<^^.>v<^v<<^><^.^^v<>.v<vv><v<v>vvv>^^>v>..<<<v..>v..<^^^<v>^^<<vv<>>^^v^.vv<><^>>.^<<^>>v.>#
+#><v..vv^<v^<>>v<>..<^>v^^><.>vv^vv^<^^v<>vv<.vv^^<>^>>^v<^^<<>^vv>v><>v<^vvv^<>><>^^^v^<v.v^<<^^>>>>><^^>><^v>>vv^v><^>^<<^.v>vv>^.v^<vv^v>>>vv>v^v<^>#
+#...>><v.<v<>^.v.v..^>^<><vv^><<<vv^<vv.><^.vv>>><v^v^>^v>>v<.^<^^<v^<>v<^<><<<.^<<vv.<>>^v^^.v>.<v>^.^>v^.v><^<<>>>^.<<<^v<<<><^>.^.^v><>^>><vv<v.<.^>#
+#<^vv>>v>v<^><^^^<^>vv<>vv>^^^.><><^>v>><v.<>vv^^<^<<<v^<><v>v^v>^<><><><><>^^>><>..^^>v<...vv<^>><.vv<^<v><v<vv^.><>v^<>v.^>>>v<<^<<^vv.>^<.^<>^<v^^^>#
+#>>^vv^.<<.<.<>>vvv<<<..<v><^<>^><<>^.<<^^^<v^<<v.<vv<^<>>vv^>.v^v<^<>>vv<<^>>.v>.v>^^^vvv^v<^><v^><>><^<.>v^^^<vv^>^v<v^<vv><>..^><.>^^<^>>..^.v^<^<v>#
+#<<><^^><v^v<^^<vv>><v..>>>^><>>>v>v>v>v><>>^vv><>>v>>vvvv<<^><>v^>vv>^.>>v.^<v<^.>>>^^v>>><vvv>><.<v<^<v<^v<v<<vvv..^^<<^<.<><<<<^<>v<<<^^>.^v>^^v<^^<#
+#>v^^^<v>^^<v<<<vv><^v.v<v^^^vvv<<><><^^><^^>>>>>><^>^^.>vv>^><<<v<<<^vv.^^^<v>v<^^^^>.^^vv<^<.<v^<vv^^^>><..><^>v><<v>v>^v^>>^^>vv.v^^^>^^vv.<<v.^><<.#
+#<^v<<^^vvv.>v>v>.v><v<^^>^>^>^^v>v^vv^<.^.>>>>>v<>.<<.<^<<vvv..<^>^><^>^<^<<>><^>v<v^v>^v^^^>>>>v>^>>^<v..><.>>^^><^<^.<v^>^.v>^^vv^v.<>>>>.v.<<>^^vv>#
+#<v^v.>.>^v>^<v.<^<^>v^>^^.>.>v<>>>^>vv<>v<>^>v^<<^<.<<^>v^<><>><^^<^^v<>>vv<<.<>v>.>^^^>><^^<^vv.><v<.<<^^>^>><>v><^vv.>v^v^v..<vvv..<<v<v^<<v>^<^>><<#
+#<^v<v^^v^>^<>v^<^<>>..>><>v<.^<.>v.>^v.>>^^<^v>>v^.v>^><>>vv.<<<>v>^.>v>..<<<v.<v^<>^>^<>v<^<v<><^>^v><.<<^^^<^.<<<^.^v^^.>^.<<vv>^v><<>^<^v^^>^v><<^>#
+######################################################################################################################################################.#

2022/tests/day24.txt

@@ -0,0 +1,6 @@
+#.######
+#>>.<^<#
+#.<..<<#
+#>v.><>#
+#<^v^^>#
+######.#