Hi,
I am trying to order elements of a vector based on heuristic values. For example, if I have a class, A, and a function,
that returns the heuristic value of A, I want to define a function that orders a vector of A based on their heuristic values -Code:int evaluate(A &input);
What is the most efficient way of doing that?Code:vector<A> *order(vector<A> *input);
Thank you very much
Code:std::sort(v.begin(),v.end(),evaluate);
"If you tell the truth, you don't have to remember anything"
-Mark Twain
Thank you very much. That works nicely.
I have a question though. It seems to me that the compare function that is passed into sort has to take two parameters by value. However, the data type that I am working with here is ~200 bytes in size, and I want to avoid passing them around by value if possible. If I define the compare function to take parameters by reference, compilation fails. Is there any workaround or alternatives?
Thank you.
The function object that std::sort takes wants to know when one element is smaller than another. My mistake. What you want is this:
And if references "won't compile," then something is wrong with your code (no offense). References are lovely. See how you can work in the above.Code:class heuristic_order { bool operator() (const A & left, const A & right) //this'll inline. { return evaluate(left) < evaluate(right); } }; // . . . . . . . . . std::sort(v.begin(),v.end(),heuristic_order());
*edit* reference problems might have to do with const-ness. Use non-constant references only when you know that you will have to modify the variable to achieve your goal (in a particular scope). Otherwise (like in comparison and "heuristic" algorithms), use constant references.
Last edited by CodeMonkey; 08-16-2007 at 12:18 AM.
"If you tell the truth, you don't have to remember anything"
-Mark Twain
Thank you very much, const-ness was indeed the problem.
