Yup. Just as I thought. Not that hard at all, and yet it still mystified me.
I got so far as the cop and robber going over, and understanding that they were the key. But the robber couldn't be left alone with anyone, and that kept stumping me. Thanks for revealing the answer so I can feel dumb, let it pass, and move on.
I think it is interesting that there are different types of cleverness (or intelligence, or whatever you want to call it). I consider myself intelligent, but there are some areas where my comprehension isn't what it could be. I'm good with words--if I read something, it is much more likely that I will understand it and recall it later. Sometimes I have an almost photographic memory. Then there are numbers. I always did well at math in school, always being put in the highest math classes, but I have a hard time visualizing large sums of money in my head--when people start talking in the thousands and millions and hundreds (like 15 hundred, which is actually one thousand five hundred), I get lost. And I have a very difficult time with foreign languages--my mind just does not seem to want to work around it. Like most people, I can read and comprehend more than I can speak. When I was younger, I had a hard time telling my right from my left. I am sure that there are other people who are weak in areas that I am strong and strong in areas that I am weak. The different areas of intelligence are interesting--there are a variety of ways to be "smart."
These types of riddles/puzzle are not my thing. But I admire those of you on the board who are problem-solvers and can figure them out.
Okay, that's enough philosophical philosophizing from me for the day.