Connect Four on 6 high, 7 wide grid, there are 4,531,985,219,092 positions for all game boards populated with 0 to 42 pieces. The game was first solved by James Dow Allen (October 1, 1988), and independently by Victor Allis (October 16, 1988). Allis describes a knowledge-based approach, with nine strategies, as a solution for Connect Four. Allen also describes winning strategies in his analysis of the game. At the time of the initial solutions for Connect Four, brute-force analysis was not deemed feasible given the game's complexity and the computer technology available at the time. Connect Four has since been solved with
Standard Borel space Standard Borel space In mathematics, a standard Borel space is the Borel space associated to a Polish space. Discounting Borel spaces of discrete Polish spaces, there is, up to isomorphism, only one standard Borel space. A measurable space is said to be "standard Borel" if there exists a metric on which makes it a complete separable metric space in such a way that is then the Borel σ-algebra. Standard Borel spaces have several useful properties that do not hold for general measurable spaces. Theorem. Let "X" be a Polish space, that is, a topological space such that there is a