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Who played first? (Posted on 2004-05-07) Difficulty: 3 of 5
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.)

See The Solution Submitted by e.g.    
Rating: 3.7000 (10 votes)

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Solution No Subject | Comment 15 of 27 |
in tic - Tac - Toe, forcing a win is impossible.

If one of the players has started in one of the corners, and the second payer did not mark the middle spot, he woudl have been forced to lose.

since the center spot is empty, the first player did not start in a corner.

the first player clearly started in the center bottom, or center top square (center right is impossible because any other second move except exactly opposite would foce a loss).

It looks like O started, since X is clearly blocking O.

So the moves are:  O - center top
X - center bottom (any other move, X loses)
O - right top
X - left top
O - right bottom
X - center right.




  Posted by Guy Soffer on 2004-05-09 12:57:18
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