Match and sort column a with column b in column c.

I have an address list in column A of 50 addresses where in column B I have routed 25 of those addresses in the order I want to visit them. I'd like to have column A rewritten in column C, but sorted in order of column B with the addresses not appearing in column b moved to the bottom of the list.

For instance

Column A:

123 Main St
456 B St
789 Alpha St
912 Blah St
987 Cup Ave
324 Yeah Cir

Column B (the route I created)

456 B St
987 Cup Ave
912 Blah St

Column C (what I want to create and need formula for...)
456 B St
987 Cup Ave
912 Blah St
123 Main St
789 Alpha St
324 Yeah Cir