Jörg Lösung für Euler 87 in Ruby

2017-03-21/jo-so_euler87.rb

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