In the Revisiting the navigation application section, you learned that a heuristic value is a property of the node, and it is a guess, or estimate, of which node will lead to the goal state quicker than others. It is a strategy used to reduce the nodes explored and reach the goal state quicker. In greedy BFS, the heuristic function computes an estimated cost to reach the goal state. For our application, the heuristic function can compute the straight-line distance to the goal state, as follows:
As you can see, in the preceding diagram the initial state is the Bus Stop. From the Bus Stop node, we have one channel, which is the Library node. Let's suppose that we're at the Library now; from the Library node, there are three child nodes: the Car Park, the Bus Stop, and the Student Center. In real life, we'd prefer to go to the Car Park, because...