36 lines
998 B
Ruby
36 lines
998 B
Ruby
require_relative 'euler'
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def bitmasks(length)
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(1..2**length-1).map { |n| n.to_s(2) }.map { |s| s.rjust(4, '0')}.map { |s| s.split('').map(&:to_i)}
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end
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def prime_digit_replacement(number, mask)
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digits = number.to_digit_list
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related_primes = []
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('0'..'9').each do |j|
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copied_digit_list = Array.new(digits)
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mask.each_with_index do |bit, index|
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copied_digit_list[index] = j if bit == 1
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end
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new_num = Euler.from_digit_list(copied_digit_list)
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related_primes.push(new_num) if new_num.prime? and !related_primes.include?(new_num) and new_num.to_digit_list.count == digits.count
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end
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related_primes
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end
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def solution(family_count)
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result = false
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Prime.take_while do |p|
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digits = p.to_digit_list
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bitmasks(digits.count).each do |mask|
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related_primes = prime_digit_replacement(p, mask)
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if related_primes.count == family_count and related_primes.include?(p)
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result = p
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break
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end
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end
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result == false
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end
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result
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end
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