Solving A Classic Interview Logic Puzzle

There are 25 mechanical horses and a single racetrack. Each horse completes the track in a pre-programmed time, and the horses all have different finishing times, unknown to you. You can race 5 horses at a time. After a race is over, you get a printout with the order the horses finished, but not the finishing times of the horses. What is the minimum number of races you need to identify the fastest 3 horses? I was suggested this puzzle via email by Terry Stickels. This is also a popular interview question at tech companies like Google. See a list of all sources in my blog post for this video: Subscribe: Send me suggestions by email (address in video). I consider all ideas though can’t always reply! Why are there comments before the video is published? Get early access and support the channel on Patreon If you buy from the links below I may receive a commission for sales. This has no effect on the price for you. Show your support! Get a mug, a t-shirt, and more at Teespring, the official site for Mind Your Decisions merchandise: My Books Mind Your Decisions: Five Book Compilation A collection of 5 books: “The Joy of Game Theory“ rated 4.1/5 stars on 44 reviews “The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias“ rated 3.5/5 stars on 4 reviews “40 Paradoxes in Logic, Probability, and Game Theory“ rated 4.4/5 stars on 13 reviews “The Best Mental Math Tricks“ rated 4.7/5 stars on 8 reviews “Multiply Numbers By Drawing Lines“ rated 4.3/5 stars on 6 reviews Mind Your Puzzles: Collection Of Volumes 1 To 3 A collection of 3 books: “Math Puzzles Volume 1“ rated 4.4/5 stars on 13 reviews “Math Puzzles Volume 2“ rated 4.5/5 stars on 6 reviews “Math Puzzles Volume 3“ rated 4.1/5 stars on 7 reviews Connect with me My Blog: Twitter: Newsletter (sent only for big news, like a new book release): 2017 Shorty Awards Nominee. Mind Your Decisions was nominated in the STEM category (Science, Technology, Engineering, and Math) along with eventual winner Bill Nye; finalists Adam Savage, Dr. Sandra Lee, Simone Giertz, Tim Peake, Unbox Therapy; and other nominees Elon Musk, Gizmoslip, Hope Jahren, Life Noggin, and Nerdwriter.