Questions from a Recruiter to a Candidate – E120

October 19, 2023 0 Comments
  1.         Starting from the back of the line (that is, with the person who can see the hat colors of all of other 99 persons), in order, and ending with the person at the head of the line (that is, with the person who can see the hat color of no one), each person exclaims either “red” or “blue”.  These exclamations can be heard by all.  Once everyone has spoken, a score is calculated, equal to the number of persons whose exclamation accurately describes their own hat color.
  2.         What strategy should the 100 persons use in order to get as high a score as possible, regardless of how the hat colors are assigned?  For example, if everyone exclaims “red”, the worst-case score is 0.  If the first 99 persons exclaim the color of the hat of the person at the head of the line and the person at the head of the line then exclaims the color he has heard, the worst-case score is 1.  If every other person exclaims the hat color of the person immediate in front and that person then repeats the color he has just heard, then the worst-case score is 50.  Can you do better? Hint: Instead of using just red and blue as the possible hat colors and exclamations, use N different colors..
  3.         A team of three people decide on a strategy for playing the following game.  Each player walks into a room.  On the way in, a fair coin is tossed for each player, deciding that player’s hat color, either red or blue.  Each player can see the hat colors of the other two players, but cannot see her own hat color.  After inspecting each other’s hat colors, each player decides on a response, one of: “I have a red hat”, “I had a blue hat”, or “I pass”.  The responses are recorded, but the responses are not shared until every player has recorded her response.  The team wins if at least one player responds with a color and every color response correctly describes the hat color of the player making the response.  In other words, the team loses if either everyone responds with “I pass” or someone responds with a color that is different from her hat color.What strategy should one use to maximize the team’s expected chance of winning?