How many possible openings are there in the game of chess, if we define an that opening consists of each player making their first 3 moves?
(With one move there are 400 possible openings)
(In reply to
En passant? by Dulanjana)
What's tricky about en passant is that it requires knowledge of the previous half-move (i.e., it must have been a two-space advance to the side of the capturing pawn in order for en passant to be legal). This complicates the state that must be stored in levik's suggested algorithm. Fortunately we can ignore pawn promotion and castling, as they can't occur within three moves. Checkmate, however, can...
re: En passant?
