Problem 92

092.rb

@@ -0,0 +1,29 @@
+require 'pp'
+
+def sum_of_squares(chains, exploration, number)
+  number = number.to_s
+  if chains.has_key?(number)
+    exploration.each do |e|
+      chains[e] = chains[number]
+    end
+    return chains
+  else
+    exploration << number
+    sum = 0
+    number.each_char { |n|
+      sum += n.to_i**2
+    }
+    return sum_of_squares(chains, exploration, sum)
+  end
+end
+
+chains = {
+  '1' => '1',
+  '89' => '89'
+}
+
+2.upto(9_999_999) do |i|
+  chains = sum_of_squares(chains, Array.new, i)
+end
+
+puts chains.select{ |k, v| v == '89' && k.to_i < 10_000_000 }.count