Thread:Raven1207/@comment-32421214-20180608012400/@comment-33669539-20180608123301

I know this one.

To simplify this, let's say there are only 2 people on the island. Let's call them A and B. The first night, they stay put since they don't know if they're the one with green eyes. The following day, they see that they didn't leave the island. So, from A's perspective, B should've left the island immediately if he saw a non-green eyed person, Person A. And due to this, he knows that he also has green eyes, which the same thing happens to person B, and so they leave on the second day.

This is extended by one day for each person there is, so 10 people would leave on the 10th day, and therefore 100 people would leave on the 100th day.