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42 lines
1.2 KiB
Python
42 lines
1.2 KiB
Python
from e007 import primes
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class NotCircular(Exception):
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pass
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def permutations(items, n):
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if n == 0:
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yield []
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else:
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for i in xrange(len(items)):
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for cc in permutations(items[:i] + items[i + 1:], n - 1):
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yield [items[i]] + cc
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def cyclic_rotation(n):
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if n < 10:
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yield n
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else:
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s = str(n)
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for i in xrange(len(s)):
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yield int(s[i:] + s[:i])
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if __name__ == '__main__':
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MAX = 1000000
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circular_primes = []
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print 'Generating primes for p < {0}...'.format(MAX)
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prime_list = primes(0, MAX)
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print 'Searching for circular primes...'
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for prime in prime_list:
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try:
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# Ensure the prime *can* be circular
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if prime > 9:
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for c in [n for n in str(prime) if n not in ['1', '3', '7', '9']]:
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raise NotCircular()
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# Check all permutations
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for rotation in cyclic_rotation(prime):
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if rotation not in prime_list:
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raise NotCircular()
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circular_primes.append(prime)
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except NotCircular:
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pass
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# Clear all permutations from the list?
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print 'Circular Primes ({0}): {1}'.format(len(circular_primes), circular_primes)
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