I'm confused. How are you trying all these if you only have two bulbs?
I can break my first bulb.
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But with my second bulb I have to go from the lowest floor (or from the lowest floor where I am sure it will not break) one by one, throw it down, check if it breaks...
If it breaks, the floor underneath is the highest floor I can throw the bulb down from without breaking it.
If it does not break, I try the next floor...
So if I throw my first bulb from floor 50, and floor 49 happens to be the highest floor from which I can throw my bulb without breaking it, I will have to try floor 1 with my second bulb, then floor 2, then floor 3, all the way to 49...
So it took me one test with the first bulb and 49 with the second bulb, a total of 50 tests...
But we want to minimize the number of tests necessary to find out which is the critical floor from which it breaks, no matter which floor it is...
So if we one by one, bottom to top from the start, we don't really use the potential of the second bulb, and we will need to do 99 tests in the worst case (if it breaks only at 100)
If we jum straight to 50, we might need 50 tests...
So the ideal is somewhere between 1 and 50, or between 2 and 40 or between 10 and 20...