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Blue-Eyed Islanders
This Hard puzzle in the “logic” category rewards careful reading and step-by-step reasoning. Use the hint if you are stuck, then compare your approach with the explained answer.
On an island, every person has either blue eyes or brown eyes.
Everyone can see everyone else’s eye color, but no one can see their own.
It is forbidden to talk about eye color.
If a person ever becomes certain that they have blue eyes, they must leave the island that night.
One day, a visitor announces publicly: “At least one of you has blue eyes.”
Suppose there are exactly 100 blue-eyed people on the island.
What happens, and when?
Preparing…