Solution
Nobody Wants Three in a Row
Show the problem again
Two players alternately write an X in any empty cell of a 3×3 grid; both write the same symbol X. A player who creates a line of three X's (row, column or diagonal) loses immediately. The first player has exactly one winning opening cell. Which cell is it? Answer 'center', 'corner' or 'edge' (naming the position type).
Worked solution
This is settled by exhaustive search of the game tree (at most 9 plies and a few thousand positions). The search shows that the first player wins, and that the centre is the only winning opening: a corner or an edge opening gives the second player a winning reply. A useful reading of the position after a centre opening is that every line through the centre is already half-built, so a later X on any of the eight outer cells makes two of the remaining cells in its lines fatal; the second player runs out of safe cells first.
Source: Notakto is a recreational misère variant of tic-tac-toe; this one-board case was solved by exhaustive search for AxiomIQ. Statement written for AxiomIQ.