43 lines
775 B
Python
43 lines
775 B
Python
#!/usr/bin/env python3
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from lib import primegen
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from fractions import Fraction
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def is_prime(n):
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return n in primes
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def Pprob(n):
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if is_prime(n):
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return Fraction(2, 3)
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return Fraction(1, 3)
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def croak(n):
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return {'P' : Pprob(n),
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'N' : 1-Pprob(n)}
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def jump(sqrs, let):
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r = [0] * len(sqrs)
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for i in range(1, len(sqrs)-1):
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prob = croak(i+1)[let] * \
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Fraction(1, 2) * sqrs[i]
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r[i+1] += prob
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r[i-1] += prob
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r[1] += sqrs[0] * croak(1)[let]
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r[-2] += sqrs[-1] * croak(len(sqrs))[let]
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return r
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def start(n):
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return [Fraction(1, n)] * n
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seq = "PPPPNNPPPNPPNPN"
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N = 500
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primes = set(primegen(N))
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sqrs = start(N)
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for letter in seq:
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sqrs = jump(sqrs, letter)
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print(sum(sqrs))
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