You have been invited to an old house with six rooms, one of which
contains a treasure. A floor plan of the house is shown below. Each room
is labelled with a letter. Some rooms are connected by doors, which are
locked. Each door is labelled with the symbol of the key that will
unlock it.
There are six rooms
labelled A, B, C, D, E and F. There are seven doors connecting the
rooms. Three of the doors are labelled with a diamond symbol, two are
labelled with a star, one with a circle, and one with a triangle. The
doors are placed as follows:
A door with a diamond connects Room A to Room B.
A door with a circle connects Room B to Room C.
A door with a star connects Room B to Room E.
A door with a star connects Room C to Room D.
A door with a diamond connects Room C to Room E.
A door with a diamond connects Room D to Room F.
A door with a triangle connects Room E to Room F.
You start in Room A and want to get to the treasure in Room F. What
is the fewest number of keys you need to get to the treasure? What are
the symbols on those keys?
