Comment Re:Coloured stamps (Score 2, Insightful) 1965
Hmm. I am not quite sure it is the solution, but I figured out that you would immediately know you have two cards of color1 on your forehead if others had 2 & 2 cards of color2 (e.g. no more color2 left for you).
If the 1st and the 3rd say they don't know and the 2nd sees that both have equal pairs of different colors (both red and both green), it means he can't have an equal pair of either color (or the 1st or the 3rd wouldve answered) and thus he has one red and one green.
If the 1st and the 3rd say they don't know and the 2nd sees that both have equal pairs of different colors (both red and both green), it means he can't have an equal pair of either color (or the 1st or the 3rd wouldve answered) and thus he has one red and one green.
