39 lines
1.2 KiB
Ruby
39 lines
1.2 KiB
Ruby
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descr=%{
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Take the number 192 and multiply it by each of 1, 2, and 3:
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192 × 1 = 192
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192 × 2 = 384
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192 × 3 = 576
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By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the concatenated product of 192 and (1,2,3)
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The same can be achieved by starting with 9 and multiplying by 1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is the concatenated product of 9 and (1,2,3,4,5).
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What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, ... , n) where n > 1?
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}
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$numbers=%q(123456789).split('').sort
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def is_pandigital(str)
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return str.split('').sort == $numbers
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end
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best=(123456789)
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(2..10).each do |n|
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concat_prod=""
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base=1
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while concat_prod.length < 10
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concat_prod=""
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(1..n).each do |i|
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concat_prod <<= (base*i).to_s
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end
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if is_pandigital(concat_prod)
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puts %{base=#{base} n=#{n} #{concat_prod}}
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if concat_prod.to_i > best
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best=concat_prod.to_i
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puts %{* base=#{base} n=#{n} #{best}}
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end
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end
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base += 1
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end
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end
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