Three castles, each occupied. One of them is king, other 2 are not. One always tells the truth, the other 2 always lie. Red and yellow castles are by the lake, green castle is not.
The three each make a statement:
Green: I am the king.
Yellow: I am not the king.
Red: The king lives by the lake.
The riddle's question: in which castle is the king?
Understood.
Answer: