The game of Tic-tac-toe is played on a large square divided into nine small squares.

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

1. Each of two players in turn places his or her mark-usually X or O - in a small square.
2. The player who first gets three marks in a horizontal, vertical, or diagonal line wins.
3. A player will always place his or her mark in a line that already contains:
   (a) two of his or her own marks or:
   (b) two of his or her opponent's marks
   thereby giving (a) priority over (b)
4. Only the last mark to be placed in the game shown above is not given.

Which mark - X or O - wins the game?

(In reply to No case to answer by Ady TZIDON)

Ady is correct.

Posted by hoodat on 2022-12-26 15:35:22