I've searched for meaning of heuristic function but everything I got is that it's function that ranks alternatives in search algorithms. But I suppose that it is not full definition of heuristics. As an example, heuristic of tree rank is used in Disjoint Union Set problem, but there's no searching!
I still don't understand, what does mean heuristic. Do you know any math definitions?
In its broadest sense, heuristics is the art of obtaining adequate results in short time from incomplete information.
As an example, the best known algorithms that solve the travelling salesman problem (i.e. finding the cheapest Hamiltonian cycle in a edge-weighted graph) have exponential time complexity. A heuristic algorithm to this problem is one that will often find a Hamiltonian cycle that is not much more expensive than the optimal solution, but will use only polynomial time.
A heuristic is a problem solving technique that comes from intuition,common sense,experience and is basically an easier and short method to solve problems.
It is applicable to human as well as machines.
Example: For example you choose to eat one of the fruits from the bucket because it looks fresh and ripe.(what you thought before picking up the fruit was an example of heuristic)
A heuristic function can be explained with an example of objective type question.
Suppose you are facing an objective test of 4 options of which only one is correct.
Now there is a question whose answer you do not know.
But then you look at the options and start thinking 1st is least probable and so is 3rd and so and so...
So basically you are rejecting least probable answers based on you experience and knwoledge related to those options
Thus it can be said that you are using a heuristic function.
Similarly for computers a heuristic function can be designed by keeping in mind the constraints of what you want from your program to do.
