Time for action – winning is everything

To determine the best course of action for the computer opponent, we need to create a prioritized list of rules for the computer to follow when deciding how to place a piece, which changes depending on the situation on the board. Let's pretend we are the computer, and we see this situation:

It wouldn't make sense to place an O anywhere but in X's way—otherwise, the computer loses. So we have our first rule:

• Block opponent from winning

Now let's look at this situation:

Sure, X is about to win, but O also has an opportunity to win. Which is more important: for O to keep X from winning, or for O to win? Clearly, it's more important for O to claim victory and win the game. So we have our second rule:

• Win

We just said that it's more important for O to claim victory than to block X, so we've also established a preferred order for these two rules:

• Win

• Block

Notice that our two statements are already written in pseudocode. Win() and Block() could just as easily be...