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Who played first? (Posted on 2004-05-07)

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.)

Submitted by e.g.

Rating: 3.7000 (10 votes)

Solution: (Hide)

Let's number the top cells 1-2-3, the middle cells 4-5-6, and the bottom cells 7-8-9.
If X were to move, he could win by playing at 4 -- and since tic-tac-toe is always a draw between experts players, then it must be O's move, and thus O played first.
If O had started at a corner, X --being a perfect player-- would have answered at the center; thus, O started at 2, and X answered either at 1 or 8. (Answering at 6 would lead to a loss.)
In both cases, the final play for X was at 6.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Puzzle Answer	K Sengupta	2022-06-22 22:30:53
X gamer	misao	2005-01-10 16:33:15
i don't know	Ashley	2004-12-26 15:07:41
No Subject	nathan	2004-09-15 06:24:58
re: Guy Soffer	Peter	2004-05-13 19:01:43
re: solved..i think	Guy Soffer	2004-05-13 03:56:36
re(2): Sum it Up	Scott	2004-05-12 18:02:14
solved..i think	Peter	2004-05-12 16:39:48
re: Sum it Up	Federico Kereki	2004-05-11 21:39:44
Sum it Up	Scott	2004-05-10 15:59:32
Starting to work...	Federico Kereki	2004-05-09 21:58:13
re: iono	Federico Kereki	2004-05-09 21:49:04
No Subject	Guy Soffer	2004-05-09 12:57:18
re: The true solution!	SilverKnight	2004-05-08 18:17:00
The true solution!	Tristan	2004-05-08 13:56:46
solution	A	2004-05-08 09:44:21
My guess	elson	2004-05-08 05:56:38
re: solution - c'mon folks	Thalamus	2004-05-08 01:55:21
bogus	Steve Royer	2004-05-08 00:57:33
solution	logischer Verstand	2004-05-08 00:00:47
iono	donnie	2004-05-07 22:54:37
iono but maybe	donnie	2004-05-07 22:50:29
re: No Subject - impossible also	Thalamus	2004-05-07 18:03:03
No Subject	Ashley	2004-05-07 17:52:46
first step or two	Tristan	2004-05-07 17:25:25
re: No Subject - impossible	Thalamus	2004-05-07 16:50:08
No Subject	Sam	2004-05-07 16:42:52

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