30 lines
689 B
Ruby
30 lines
689 B
Ruby
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#!/usr/bin/ruby -W
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# coding: utf-8
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#
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# Copyright © 2017 Jörg Sommer <joerg@alea.gnuu.de>
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#
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# License: MIT https://opensource.org/licenses/MIT
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######
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##
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## Solution of Euler 87 https://projecteuler.net/problem=87
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##
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require 'prime'
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LIMIT = 50_000_000
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primesPower2 = Prime.each(Math.sqrt(LIMIT)).map { |e| e ** 2 }
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primesPower3 = Prime.each(Math.cbrt(LIMIT)).map { |e| e ** 3 }
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primesPower4 = Prime.each(LIMIT ** (1.0/4)).map { |e| e ** 4 }
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ans = primesPower2.product(primesPower3) \
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.map { |a, b| a + b } \
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.select { |e| e < LIMIT } \
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.product(primesPower4) \
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.map { |a, b| a + b } \
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.select { |e| e < LIMIT } \
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.uniq \
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.size
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puts 'Answer: ' + ans.to_s
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