43 lines
830 B
Python
43 lines
830 B
Python
''' The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.
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There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.
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How many circular primes are there below one million? '''
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from math import log10
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pp = [2]
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for i in xrange(3, 1000, 2):
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for x in pp:
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if i % x == 0:
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break
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else:
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pp.append(i)
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def isp(a):
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for i in pp:
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if a % i == 0:
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if a == i:
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return True
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return False
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return True
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def loop(x):
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length = int(log10(x))
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return (x % 10) * 10 ** length + x / 10
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def lote(n):
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tt = n
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while 1:
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if not isp(tt):
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return False
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tt = loop(tt)
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if tt == n:
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return True
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out = [2]
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for ii in xrange(3, 1000000, 2):
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if lote(ii):
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out.append(ii)
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print len(out)
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