Department: the Waiting Room
EASY The diagram above represents a city street map. One police officer is positioned at the red dot. Add one more officer so that every point on every street can be seen by at least one of the two patrolmen. Officers can see only down the streets; tall buildings prevent them from seeing across the blocks.
CHALLENGING Position three police officers at separate locations on the map so every point on every street can be seen by at least one officer. To solve the problem, two of the officers must be able to see each other.
DIFFICULT Position four police officers on the map so that every point on every street can be seen by at least one officer. Hint: Three of the officers are on the same street.