The king and the slaves
Brown eyes - the slave speaks the truth
Blue eyes - the slave lies
If the first slave has brown eyes, he will say that he has brown eyes.
If the first slave has blue eyes, he will say that he has brown eyes (for they lie).
In asking the second slave in line, he replied that the first had said he had blue eyes. Therefore, the second slave is a liar! So we conclude that the second one has blue eyes.
The third slave said the first one has brown eyes and the second one has blue eyes. As we have already concluded that the second has blue eyes, so the third speaks the truth, and therefore has brown eyes. And from his statement, we conclude that the former has brown eyes as well.
Therefore, as there were only two brown-eyed slaves, the others have blue eyes. The queue was as follows:
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