Given a tic-tac-toe board as input, where the game may already be started:
| |
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|X|
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Output a tic-tac-toe board with the best possible move for the player whose next turn it is. You can assume a well-formed board (you won't have just 3 Os):
| |O
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|X|
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The only acceptable moves here are corners, since if you put it on the side X can force a win.
Smallest character count wins!