I am a teacher who was given a problem a few years ago. Every year since I have given it to my advanced students as a bonus assignment, but in ~10 years only 8 solved it, each with a slightly different approach. The problem is as follows:

You have some input, in the following format (minus //comments):

6 //Route Begin 1 2 //Route data... 1 3 3 4 3 5 4 6 5 6 2 3 2 4 0 0 //Route end 4 //Route Begin 2 3 //Route Data... 3 4 5 1 1 6 7 8 8 9 2 5 5 7 3 1 1 8 4 6 6 9 0 0 //Route end // continued... 

The input begins with the destination, an integer. It is followed by a 'map' of all streets in the city. Each line represents a connection, so you can get from street 1 to street 2, and vice-versa. On every rout you start at street 1, then work your way to your destination.

The objective: List all possible routes, and tell the user the shortest one (least amount of street changes). So you would wont to output something like:

Destination 1 (6): 1 2 3 4 6 1 2 3 5 6 1 2 4 3 5 6 1 2 4 6 1 3 2 4 6 1 3 4 6 1 3 5 6 There are 7 routes from the fire station to street 6. The shortest of these is the route "1 2 4 6", with 4 streets. Destination 2 (4): 1 3 2 5 7 8 9 6 4 1 3 4 1 5 2 3 4 1 5 7 8 9 6 4 1 6 4 1 6 9 8 7 5 2 3 4 1 8 7 5 2 3 4 1 8 9 6 4 There are 8 routes from the fire station to street 4. The shortest of these is the route "1 3 4", with 3 streets. 

Now personally, I rather java or python (and java is preferred more), but I leave this open ended to my students, so they can choose any language they like.

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