Kees van Kempen
efe6e5a0c3
It takes 10 - 20 minutes to solve it. It is too slow. It seems that List.count takes too long.
66 lines
1.6 KiB
Python
66 lines
1.6 KiB
Python
from part1 import *
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verbose = False
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thoughts = \
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"""
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So, we can place an obstacle on each of the 130*130 - #obstacles = 16900
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- obstacles positions, but the initial path only covers 1512 positions
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(thus 1512 - 1 = 1511 steps). By instead placing an obstacle on each of
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those steps, we can find a loop.
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The other thing we need to do, is detect loops. For that, It would be
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nice to store both positions and directions to establish uniqueness,
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or just check whether it is the fifth time in a position (as we have
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then travelled to that position at least twice from at least one
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position; see Pigeonhole principle).
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"""
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if __name__ == "__main__":
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m = Map()
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#m.load_map("testinput")
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m.load_map("input")
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# Prepare forked map for speed
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forked_map = m.copy()
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#forked_map = Map()
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#forked_map.load_map("input")
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begin_pos = m.pos
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begin_direction = m.direction
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loop_obstacles = []
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i = 0
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while m.step():
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print(i)
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if verbose:
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print(m.pos, m.direction)
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# Create a copy
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#forked_map = m.copy()
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#forked_map = Map()
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#forked_map.load_map("input")
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#forked_map.map = m.map.copy()
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forked_map.map[m.next_pos()] = Map.Tiles.OBSTACLE.value
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forked_map.map[m.pos] = m.map[m.pos]
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forked_map.pos = begin_pos
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forked_map.direction = begin_direction
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forked_map.trace = [begin_pos]
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print(f"Forking at {forked_map.next_pos()}... ", end="")
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try:
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while forked_map.step():
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continue
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except Map.LoopException:
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print("loop.")
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loop_obstacles.append(m.next_pos())
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else:
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print("no loop.")
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i += 1
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if i > 100:
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break
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#m.show()
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#print(len(m.trace), m.trace)
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#print(len(set(m.trace)))
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print(len(loop_obstacles))
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