61 lines
1.3 KiB
Python
61 lines
1.3 KiB
Python
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""" day 6 part 1 """
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import fileinput
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room = [list(line.strip()) for line in fileinput.input()]
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start_pos = None
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for y,line in enumerate(room):
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for x,cell in enumerate(line):
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if cell in '^<>v':
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start_pos=(x,y,cell)
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dirs = {
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'^': (0,-1,'>'),
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'>': (1,0,'v'),
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'v': (0,1,'<'),
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'<': (-1,0,'^')
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}
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def will_loop(room):
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visited = set()
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guard_x, guard_y, guard_d = start_pos
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while 0 <= guard_y < len(room) and 0 <= guard_x < len(room[guard_y]):
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dx, dy, turn = dirs[guard_d]
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# print(guard_x,guard_y,guard_d)
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step_x = guard_x + dx
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step_y = guard_y + dy
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if 0 <= step_y < len(room) and 0 <= step_x < len(room[step_y]) and room[step_y][step_x] == '#':
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guard_d = turn
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else:
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if (guard_x,guard_y,guard_d) in visited:
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return True, visited
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visited.add((guard_x,guard_y,guard_d))
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guard_x,guard_y = step_x,step_y
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return False, visited
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_, path = will_loop(room)
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loops = 0
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candidates = {(x,y) for x,y,_ in path}
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print(len(candidates), candidates)
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for x,y in candidates:
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if room[y][x] == '.':
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room[y][x] = '#'
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# print('\n'.join([''.join(line) for line in room]))
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if will_loop(room)[0]:
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print('loop',x,y)
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loops += 1
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room[y][x] = '.'
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print(loops)
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