(1) might not always find the best solution
(2) but is guaranteed to find a good solution in a reasonable time
(1) could not be solved any other way
(2) solutions take an infinite time or very long time to compute
A heuristic is a function that, when applied to a state, returns a number
that is an estimate of the merit of the state, with respect to the goal.
we often call it H function…
Then, we can use these value to guide us to make the decision.
the decision is not guaranteed best…