It is saying that you should use a brute force approach, going through every single possible state of the switches. Say you have 2 switches, That means there are 2^2 = 4 different states, namely 00, 01, 10, and 11 (where 1 represents ON and 0 represents OFF), Because the bounds are so low, even with an exponential complexity you should be able to solve the question with this approach.

a.k,a

• iterate through all possible states as binary numbers
• check for all states whether all the lightbulbs would be on or not