Question

I want to construct three different priority_queue‘s that hold a class Thing and then sort each one differently by values that are held by the Thing. I know that I can define an operator method either internally, or a friend to the object, but is there a way to have it use different test method(s)? How do I tell it to use that method instead of the operator method? And how would the parameter list differ from creating an operator overload?

Answer 1

Like most STL containers, the priority_queue accepts a Compare class in its template arguments.

struct MyCompare1 {
  bool operator()(const Thing& t1, const Thing& t2) {
    // your logic here
  }
};

std::priority_queue<Thing, std::vector<Thing>, MyCompare1> my_queue;