Given this tic-tac-toe position, as played by two expert players, who went first and where? Also, which was the last "move"?

 X | O | O 
---+---+---
   |   | X
---+---+---
   | X | O

(An expert player is a player who would never play in such a way that would allow his opponent to win, and who would also try to get the possible best result.)

Expert Player = One who always tries to force a win and never allows a forced loss.

*All games tie per two expert players*

*First move cannot be a corner because the second player would have had to go middle to prevent an win*

*X did not go first since going West on next move would have set up a forced win*

-> Therefore, first move: O, North.

X's response:

South? No because O will in effect go Middle and force a win.
East? No because, once again, O goes Middle, game over.

-> Therefore, 2nd move: X, Northwest.

O's response:

Northeast? No because if X goes center, game over.

-> Therefore, 3rd move: O, Southeast.

X's Response:

East? No because if O goes South, game over.

-> Therefore, 4th move: X, South.

Finally, 5th move: O, Northeast & 6th move: X, East.

I know the right answer has been given already by Tristan and Guy, but I just wanted to show my logic. :D

Posted by Scott on 2004-05-10 15:59:32