>>The king smurf gathered all the smurfs of his land to play a game. 100 smurfs assembled in his great hall and listened attentively to the king. "I will either place a red hat or a gree>
>It´s a nice inductive solution, and here it goes:
>
>If there had been only one green hat, on the first day that smurf, seeing 99 red hats, would have known his hat was green. Since it didn´t happen, there were at least 2 green hats.
>
>If there had been only two green hats, on the second day the green hat smurfs, seeing 98 red ones and 1 green (and reasoning that there had to be at least 2 green hats as seen previously) would have known that they had green hats. Since it didn't happen, there were at least 3 green hats.
>
>Do I need to go on?
>
>Nice problem!

That's correct :)