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Tic tac toe variation (Posted on 2019-07-22) Difficulty: 1 of 5
Ann and Beth play tic tac toe with a variation, if you get three in a row, you LOSE and everyone plays with only X (not X and O). If both players play optimally, and Ann goes first, then who will win?

No Solution Yet Submitted by Danish Ahmed Khan    
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Solution Not D1 solution Comment 1 of 1
If there's a simple way to do this, I didn't find it.  Basically I had to draw out every board position to find which are W or L.  (There are 42 board positions with no three-in-a-row, not counting reflections/rotations.)

The only way for Ann to win is to play first in the center square.  

Board after Play 1:
---
-X-
---
Either Play 2 is countered by Play 3 which can bring the board to:
X--
-X-
-X-
There are four possible Play 4 but Play 5 can always bring the board to:
X--
-XX
XX-
The 6th play will create three-in-a-row.

Edited on July 23, 2019, 11:12 am
  Posted by Jer on 2019-07-23 11:09:32

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