You are standing on the first floor of a house. Next to you are three light switches that are connected to three lights upstairs. Your challenge is to figure out which light switch downstairs is connected to which of the three lights upstairs given the following constraints:
You must start downstairs.
You can flip the three light switches any way you want while you are downstairs.
You are allowed only one trip upstairs and while upstairs you have to decide which switch is con- nected to which light.