Question 21
The diagram represents a neighbourhood’s lamps. Switching on one lamp also lights every lamp directly connected to it. Initially all are off. What is the least number of switches that must be selected to light every lamp?
A selected switch lights that lamp and its immediate neighbours only; lamps lit indirectly do not trigger further automatic switches.
A selected switch lights that lamp and its immediate neighbours only; lamps lit indirectly do not trigger further automatic switches.