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Message: [QUOTE="Simon Strandgaard, post: 4495078"] [snip] I could not find any fast solution.. -- Simon Strandgaard # Weird Numbers # Simon Strandgaard <neoneye@gmail.com> def divisors(value) ary =3D [] (value/2).times do |i| div =3D i + 1 ary << div if value % div =3D=3D 0 end ary end $bits =3D [] 32.times do |bit| $bits << 2 ** bit end def has_subset_equal_to(divs, value) pairs =3D divs.zip($bits) 1.upto(2 ** divs.size - 1) do |i| sum =3D 0 pairs.each{|div,b| sum+=3Ddiv if (i&b)>0 } return true if sum =3D=3D value end false end def find_weird_numbers(range_min, range_max) ary =3D [] range_min.upto(range_max) do |value| divs =3D divisors(value) sum =3D divs.inject(0){|a,b|a+b} ary << [value, divs] if sum > value end res =3D [] ary.each do |value, divs| if !has_subset_equal_to(divs, value) puts "##{value} is a WEIRD NUMBER" res << value else puts "##{value} is nothing" end end p res end p find_weird_numbers(1, 100) [/QUOTE]