32 lines
739 B
Python
32 lines
739 B
Python
def solution(start, length):
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checksum = 0
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for i in range(length):
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base = start + length * i
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checksum ^= calc_checksum_range(base, base + length - i)
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return checksum
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# P = [01]*
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# P^P = 0
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# P00^P01^P10^P11 = 0
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def calc_checksum_range(_from, _to): # _from included, _to is NOT included
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checksum = 0
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remain = (-_from) % 4
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for i in range(_from, min(_from + remain, _to)):
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checksum ^= i
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checkpoint = _from + remain
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remain = _to % 4
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for i in range(max(_from, checkpoint, _to - remain), _to):
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checksum ^= i
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return checksum
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tests = [
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([0, 3], 2),
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([17, 4], 14)
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]
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for i, o in tests:
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result = solution(*i)
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print (i, result == o, result, o)
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