My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2016/18
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2016/day18.py
+52
2016/day18.py
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import fileinput
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def is_safe(row, x):
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"""Helper function to read out-of-bounds tiles as safe."""
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if x < 0 or x >= len(row):
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return True
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return row[x]
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def predict_next_row(row):
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"""Given a row, returns the predicted following row."""
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next_row = []
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for i in range(len(row)):
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a, b, c = (is_safe(row, x) for x in range(i-1, i+2))
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next_row.append(predict_safe(a, b, c))
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return tuple(next_row)
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def predict_safe(a, b, c):
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if a and b and not c:
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return False
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elif not a and b and c:
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return False
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elif a and not b and not c:
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return False
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elif not a and not b and c:
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return False
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return True
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if __name__ == '__main__':
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# Represent safe tiles as True and traps as False
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raw_first_row = fileinput.input()[0].strip()
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row = tuple(True if c == '.' else False for c in raw_first_row)
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safe_tiles = sum(row)
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for _ in range(40 - 1):
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row = predict_next_row(row)
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safe_tiles += sum(row)
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print "Number of safe tiles in first 40 rows:", safe_tiles
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for _ in range(400000 - 40):
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row = predict_next_row(row)
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safe_tiles += sum(row)
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print "Number of safe tiles in all 400000 rows:", safe_tiles
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2016/inputs/18.txt
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2016/inputs/18.txt
···
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...^^^^^..^...^...^^^^^^...^.^^^.^.^.^^.^^^.....^.^^^...^^^^^^.....^.^^...^^^^^...^.^^^.^^......^^^^