graduate program interview questions shared by candidates
"You have 25 horses, no stop watch, and you can only race 5 horses at a time. What is the minimum number of races you need in order to find the fastest horse? How would you find the second fastest horse?"
Hold 5 races, each of 5 new horses, then have a final 6th race which races all the winners of the previous 5 races. Answer: 6 races To find the second fastest, the process is the same as before except race the 2nd fastest horses from each race, the fastest horse of all the 2nd place horses is the overall second fastest.
Surely there is more to determining the second fastest horse overall... Having found the fastest horse using the method described above, after the 6th race, one would be left the fastest horse, the 4 losing horses from the 6th race and 20 other horses defeated in the first round of races. The second fastest horse is not the horse that came second in the 6th race, because there is a chance that the second fastest horse overall could have been in the same race as the eventual overall winner in the first round of races (thereby not progressing to the 6th race despite being faster than the 4 of the horses in the 6th race). Answer: So to be sure of identifying the second fastest horse overall you would have an 7th race of all the second placed horses from the first 5 races. Then, you would hold an 8th race in which the winner of the 7th race competes against the 4 losing horses from the 6th race. The winner of this race would be the second fastest overall.
Have 6 races as above for the fastest horse. Say the fastest horse overall initially won the 3rd race, then to find the 2nd fastest horse, you race the 2nd place horse from the 3rd race with the four losing horses (i.e. the four winning horses in races 1, 2, 4 & 5) from the 6th race. The winner of this 7th race is the 2nd fastest horse
Telephone interview: - Which start-up could Dropbox acquire? - What would you change in the Dropbox app? On-site interviews: - Samsung and Dropbox have a deal so that on each Samsung cell phone that is bought, the Dropbox app is already installed. In one year, in France (I'm French), how many new accounts are created thanks to that relationship? - How would you explain cloud storage to somebody who does not know anything about computers?