Question

I am trying to implement a min heap in c++ for a struct type that I created. I created a vector of the type, but it crashed when I used make_heap on it, which is understandable because it doesn’t know how to compare the items in the heap. How do I create a min-heap (that is, the top element is always the smallest one in the heap) for a struct type?

The struct is below:

struct DOC{

int docid;
double rank;

};

I want to compare the DOC structures using the rank member. How would I do this?

I tried using a priority queue with a comparator class, but that also crashed, and it also seems silly to use a data structure which uses a heap as its underlying basis when what I really need is a heap anyway.

Thank you very much,
bsg

Answer 1

Add a comparison operator:

struct DOC{

    int docid;
    double rank;
    bool operator<( const DOC & d ) const {
       return rank < d.rank;
    }
};

Structures can almost always usefully have a constructor, so I would also add:

DOC( int i, double r ) : docid(i), rank(r) {]

to the struct as well.