Problem 71

071.rb

@@ -0,0 +1,23 @@
+require 'pp'
+
+too_big = 3.0/7
+fractions = [["2/5", 0.4], ["3/7", too_big]]
+existing_fractions = {"2/5" => true, "3/7" => true}
+closest = 0.4
+
+2.upto(1_000_000) do |d|
+  ((d*closest).to_i).upto(d-1) do |n|
+    calculation = n.to_f/d
+    break if calculation > too_big
+    unless existing_fractions[calculation.to_s]
+      fractions << ["#{n}/#{d}", calculation]
+      existing_fractions[calculation.to_s] = true
+      closest = calculation if calculation > closest
+    end
+  end
+  pp "Finished Processing #{d}: # of fractions #{existing_fractions.count}" if d % 1_000 == 0
+end
+
+fractions.sort!{ |a, b| a[1] <=> b[1] }
+three_sevenths_index = fractions.find_index{|f| f[0] == '3/7'}
+pp fractions[three_sevenths_index-1][0]