There’s an interesting mind-teaser/puzzle that floats around the internet in waves. Sometimes it’s described as a Google interview question; sometimes it’s described as a Microsoft interview question. No matter of the origin, it’s a fun little critical thinking puzzle and in this blog posting I’m going to look into it and take it a little further …

You are given two eggs, and access to a 100-storey building. Both eggs are identical. The aim is to find out the highest floor from which an egg will not break when dropped out of a window from that floor. If an egg is dropped and does not break, it is undamaged and can be dropped again. However, once an egg is broken, that’s it for that egg.

If an egg breaks when dropped from floor n, then it would also have broken from any floor above that. If an egg survives a fall, then it will survive any fall shorter than that.

The question is: What strategy should you adopt to minimize the number egg drops it takes to find the solution?. (And what is the worst case for the number of drops it will take?)