In the first two topics, we learned how to define an intelligent agent, and how to create a heuristic that guides the agent toward a desired state. We learned that this was not perfect, because at times we ignored a few winning states in favor of a few losing states.

We will now learn a structured and optimal approach so that we can execute a search for finding the shortest path between the current state and the goal state: the A* ("A star" instead of "A asterisk") algorithm:

Figure 2.3: Finding the shortest path in a maze

For a human, it is simple to find the shortest path, by merely looking at the image. We can conclude that there are two potential candidates for the shortest path: route one starts upwards, and route two starts to the left. However, the AI does not know about these options. In fact, the most logical first step for a computer player would be moving to the square denoted by the number 3 in the following diagram:

Why? Because this is the only...