How to generalize a method inside a class - c++

Question

I have a class called MinPQ (priority queue) which works on generic data called Item. Out of the greater() method, other methods are doing work on the indexes of the items.
The greater() method is comparing two different items - see bellow.
This method will work fine for any standard data type (Item = int, float, etc...) but what about a user defined object?
How can I modify this MinPQ class and the greater() method in order to take into account a more general Object?
The MinPQ class:
template <class Item> class MinPQ
{
private:
Item *items;
int N;
int queueSize;
void resize(int capacity);
void swim(int k);
bool greater(int i, int j);
void exch(int i, int j);
void sink(int k);
public:
MinPQ();
MinPQ(const MinPQ &pq);//copy constructor
~MinPQ();
void insert(Item item);
Item min();
inline int size(){return N-1;}
inline bool isEmpty(){return size() == 0;}
void print();
};
the constructors:
template <class Item> MinPQ<Item>::MinPQ(const MinPQ &pq)
{
N = pq.N;
queueSize = pq.queueSize;
items = new Item[queueSize];
for(int i = 0; i < N; ++i)
items[i] = pq.items[i];
}
template <class Item> MinPQ<Item>::MinPQ()
{
queueSize = 2;
items = new Item[queueSize];
N = 1;
}
The greater() method:
template <class Item> bool MinPQ<Item>::greater(int i, int j)
{
return items[i] > items[j];
}

Answer 1

Having the definition of SomeItem you can specify that operator > will do with two items:
struct SomeItem
{
//item stuff
int item_property;
};
bool operator > (const SomeItem & a,const SomeItem & b)
{
return a.item_property > b.item_property;
}
//after this you can compare items based on item_property.
//...
MinPQ<SomeItem> a;
a.greather(0,1);//this will work as long as types used int MinPQ will have operator >
Or you can overload the operator directly inside the type:
struct SomeItem
{
//item stuff
int item_property;
bool operator > (const SomeItem & other)const
{
return item_property > other.item_property;
}
};