30 lines
778 B
Python
30 lines
778 B
Python
def p(leading_digits, count):
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n_cutoff = 18
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leading_digits_str = str(leading_digits)
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n_digits = len(leading_digits_str)
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j, current_leading, found = 1, 2, 0
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while found < count:
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current_leading *= 2
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j += 1
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current_leading_str = str(current_leading)
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if current_leading_str[:n_digits] == leading_digits_str:
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found += 1
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current_leading = int(current_leading_str[:n_cutoff])
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return j
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def euler_686():
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assert p(12, 1) == 7
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assert p(12, 2) == 80
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assert p(123, 45) == 12710
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assert p(123, 100) == 28343
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assert p(123, 1000) == 284168
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return p(123, 678910)
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if __name__ == "__main__":
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solution = euler_686()
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print("e686.py: " + str(solution))
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assert solution == 193060223
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