stl priority_queue organization?

[mistersteve]

Ok, so I've just written my first program that uses the stl priority_queue. Everything went pretty well, except I have no idea how to get my stuff to "pop" out in the order I want! I know that i automatically organizes its contents from smaller to larger, but I am storing instances of a structure, and it seems to just toss them back out in the order they were entered. HOW can manipulate the order in which it returns my structure instances??

Any help would be greatly appreciated. Thanks everyone.

[JosAH]

Ok, so I've just written my first program that uses the stl priority_queue. Everything went pretty well, except I have no idea how to get my stuff to "pop" out in the order I want! I know that i automatically organizes its contents from smaller to larger, but I am storing instances of a structure, and it seems to just toss them back out in the order they were entered. HOW can manipulate the order in which it returns my structure instances??

Any help would be greatly appreciated. Thanks everyone.

What exactly did you do? a) did you supply a comparison object to your
priority_queue? or b) did you overload the < operator in your struct?

kind regards,

Jos

[mistersteve]

Haha, I didn't do either one of those. I have no idea what that even means. But that sounds like a pretty good idea! Do you mind showing me how? (if that can be done without expending too much of your time, of course.)

[JosAH]

Haha, I didn't do either one of those. I have no idea what that even means. But that sounds like a pretty good idea! Do you mind showing me how? (if that can be done without expending too much of your time, of course.)

Well you have to have a notion of which struct has higher priority than another
struct. The one with the highest priority will come out of the heap first. If A < B
is true than struct A has higher priority than struct B.

All you have to do is overload the operator< for your struct. Something like this:

boolean operator<(struct& B) {
   // this struct is A, so implement A < B
}
 

kind regards,

Jos

[mistersteve]

Well you have to have a notion of which struct has higher priority than another
struct. The one with the highest priority will come out of the heap first. If A < B
is true than struct A has higher priority than struct B.

All you have to do is overload the operator< for your struct. Something like this:

boolean operator<(struct& B) {
   // this struct is A, so implement A < B
}
 

kind regards,

Jos

I am trying very hard to understand. Haha, I really am. I only have one struct. But I am storing in my priority_queue many different instances of that struct. Each instance contains the information about a given appointment (the purpose of this program is to keep and appointment book). So my struc looks something like this:

struct book {
              string lastName, firstName, date, hours, minutes, ampm;
              int idTag;
};
 

So when i run the program, it asks for information reguarding any number of patients (or whoever is making appointments to see me) I enter their first name, last name, the date and time of the appointment, then the program pushes that instance into my priority_queue, and I start entering information about the next appointment. Now, when I start to pop, I want it to spit out the appointments starting with the soonest, and moving down to list to the most distant one. This is why I included the int idTag in my struct. Each appointment has an "id number" so that they can be ordered so, if I have an appointment on November 5th, at 3:30pm, that instance's idTag will be 11051530.

Basically, what I can't figure out how to do is get my priority_queue to sort and pop my instances according one variable within each instance (i want it to look at each instance's idTag to decide what order they should be popped in). If i am going about this totally the wrong way, I'll be happy to recieve any correction! I just feel like I'm pretty close... maybe. heh.

Thanks for your patience,
mistersteve