Insight · ★★★☆☆ · ~7 min
Rainbow Hats (Simultaneous Guessing)
N people, N colors, guess simultaneously. Guarantee at least one is right.
by MindYourPuzzle
N people enter a room. Each gets a hat labeled with one of the numbers 1–N (duplicates allowed). Everyone sees everyone else's hat but not their own. All simultaneously guess their own number.
What strategy guarantees at least one correct guess?
Hints