1 files changed, 41 insertions, 0 deletions
diff --git a/challenge-147/roger-bell-west/ruby/ch-2.rb b/challenge-147/roger-bell-west/ruby/ch-2.rb
new file mode 100755
index 0000000000..0c79ae306e
--- /dev/null
+++ b/challenge-147/roger-bell-west/ruby/ch-2.rb
@@ -0,0 +1,41 @@
+#! /usr/bin/ruby
+
+def pentagon(n)
+  return (n*(3*n-1)/2).to_i
+end
+
+def pentpair()
+  fpent=[0]
+  rpent=Hash.new
+  mx=0
+  a=1
+  while 1 do
+    while mx < a do
+      mx += 1
+      fpent.push(pentagon(mx))
+      rpent[fpent[mx]]=mx
+    end
+    1.upto(a-1) do |b|
+      d=fpent[a]-fpent[b]
+      if d < fpent[b] then
+        break
+      end
+      if rpent.has_key?(d) then
+        s=fpent[a]+fpent[b]
+        while s > fpent[mx] do
+          mx += 1
+          fpent.push(pentagon(mx))
+          rpent[fpent[mx]]=mx
+        end
+        if rpent.has_key?(s) then
+          print("P(#{a}) + P(#{b}) = #{fpent[a]} + #{fpent[b]} = #{s} = P(#{rpent[s]})\n")
+          print("P(#{a}) - P(#{b}) = #{fpent[a]} - #{fpent[b]} = #{d} = P(#{rpent[d]})\n")
+          exit(0)
+        end
+      end
+    end
+    a += 1
+  end
+end
+
+pentpair()