Day 23

23.input

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+#############
+#...........#
+###C#B#D#A###
+  #B#D#A#C#
+  #########

23.py

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+from more_itertools import flatten
+from queue import PriorityQueue
+#############
+#01.4.7.A.DE#
+###2#5#8#B###
+  #3#6#9#C#
+  #########
+
+blank_map = """#############
+#...........#
+###.#.#.#.###
+  #.#.#.#.#
+  #########"""
+
+final_map = """#############
+#...........#
+###A#B#C#D###
+  #A#B#C#D#
+  #########"""
+
+from util import get_input
+input = get_input("23.input", lambda a: a)
+
+top_row = [(1, 1), (2, 1), (4, 1), (6, 1), (8, 1), (10, 1), (11, 1)]
+
+columns = {
+        'A': [(3, 2), (3, 3)],
+        'B': [(5, 2), (5, 3)],
+        'C': [(7, 2), (7, 3)],
+        'D': [(9, 2), (9, 3)],
+        }
+
+state_map = list(flatten([col for col in columns.values()])) + top_row
+
+cost = {'A': 1, 'B': 10, 'C': 100, 'D': 1000}
+
+def map_to_state(m, state_map):
+    state = list()
+    for (x, y) in state_map:
+        state.append(m[y][x])
+    return tuple(state)
+
+def state_to_map(state, state_map, blank_map):
+    m = [[c for c in line] for line in blank_map.splitlines()]
+    state = list(state)
+    for i, (x, y) in enumerate(state_map):
+        m[y][x] = state[i]
+    return m
+
+def neighbors(pos, m):
+    (x, y) = pos
+    return [(x + dx, y + dy) for (dx, dy) in [(-1, 0), (1, 0), (0, -1), (0, 1)] if m[y + dy][x + dx] == '.']
+
+def try_walk(pos, m, dests, visited, dist):
+    res = list()
+    if pos in dests and dist > 0:
+        res.append((pos, dist))
+    for n in neighbors(pos, m):
+        if n in visited:
+            continue
+        res += try_walk(n, m, dests, visited + [n], dist + 1)
+    return res
+
+def all_moves(pos, m, columns):
+    (x, y) = pos
+    a = m[y][x]
+    if a == '.':
+        return []
+    col = columns[a]
+    if pos in col and all([m[y][x] == a for (x, y) in col[col.index(pos):]]):
+        return []
+    dests = []
+    for c in columns.values():
+        if pos in c:
+            dests += top_row
+            break
+    if all([m[y][x] in [a, '.'] for (x, y) in col]):
+        dests.append([(x, y) for (x, y) in col if m[y][x] == '.'][-1])
+    return try_walk(pos, m, dests, [pos], 0)
+
+
+def next_states(state, state_map, blank_map, columns):
+    state = list(state)
+
+    res = list()
+    m = state_to_map(state, state_map, blank_map)
+
+    for i, a in enumerate(state):
+        for dest, dist in all_moves(state_map[i], m, columns):
+            new_state = list(state)
+            new_state[i] = '.'
+            new_state[state_map.index(dest)] = a
+            res.append((tuple(new_state), dist * cost[a]))
+
+    return res
+
+def state_search(state, blank_map, final_map, state_map, columns):
+    final_state = map_to_state(final_map.splitlines(), state_map)
+    dist_map = {state: 0}
+    queue = PriorityQueue()
+    queue.put((0, state))
+    while not queue.empty():
+        (d, state) = queue.get()
+        dist = dist_map[state]
+        for (next_state, ndist) in next_states(state, state_map, blank_map, columns):
+            if dist + ndist < dist_map.get(next_state, 99999999):
+                dist_map[next_state] = dist + ndist
+                queue.put((dist + ndist, next_state))
+    return dist_map[final_state]
+
+state = map_to_state(input, state_map)
+
+print("Part 1:", state_search(state, blank_map, final_map, state_map, columns))
+
+columns = {
+        'A': [(3, 2), (3, 3),(3, 4), (3, 5)],
+        'B': [(5, 2), (5, 3),(5, 4), (5, 5)],
+        'C': [(7, 2), (7, 3),(7, 4), (7, 5)],
+        'D': [(9, 2), (9, 3),(9, 4), (9, 5)],
+        }
+
+state_map = list(flatten([col for col in columns.values()])) + top_row
+
+blank_map = """#############
+#...........#
+###.#.#.#.###
+  #.#.#.#.#
+  #.#.#.#.#
+  #.#.#.#.#
+  #########"""
+
+final_map = """#############
+#...........#
+###A#B#C#D###
+  #A#B#C#D#
+  #A#B#C#D#
+  #A#B#C#D#
+  #########"""
+
+extra_in = """  #D#C#B#A#
+  #D#B#A#C#
+""".splitlines()
+
+state = map_to_state(input[0:3] + extra_in + input[3:], state_map)
+
+print("Part 2:", state_search(state, blank_map, final_map, state_map, columns))

23.small.input

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+#############
+#...........#
+###B#C#B#D###
+  #A#D#C#A#
+  #########