for pointers you must do the following(2 modifications that you must do):
include<iostream>
#include<vector>
#include<queue>
using namespace std;
int j;
class vertex
{
public:
vertex *parent;
int value;
vertex()
{
parent = NULL;
value=++j;
}
~vertex();
};
//define your own comparison predicate:
struct vertex_compare : binary_function<vertex*, vertex*, bool>
{
bool operator()(const vertex* v1, const vertex* v2) const
{
return (v1->value > v2->value);
}
};
int main()
{
int i;
vertex *array;
//and now use this comparison predicate
priority_queue<vertex *,vector<vertex *>,vertex_compare > Q;
//now can insert your elements of type vertex in pq
for(i=0;i<9;++i)
{ array = new vertex;
Q.push(array);}
//now Q.top() will give the minimum value
while(!Q.empty()){
cout<<endl<<Q.top()->value;
Q.pop();}
cout<<endl<<endl;
system("PAUSE");
}
On Sun, Jun 15, 2008 at 1:42 PM, Pratyush <[EMAIL PROTECTED]> wrote:
>
> Thankyou Shaarang this helped me a lot and raised another doubt. I
> think you can help me further...
> instead of the array of object I now used class pointers and created
> some objects dynamically.
> I modified the PQ decalration to hold pointers but i get an unexpected
> result..
> here's what i did
>
> #include<iostream>
> #include<vector>
> #include<queue>
> using namespace std;
> int j;
> class vertex
> {
> public:
> vertex *parent;
> int value;
> vertex()
> {
> parent = NULL;
> value=++j;
> }
> ~vertex();
> };
>
> bool operator < (const vertex& v1, const vertex& v2)
> {
> return (v1.value > v2.value);
> }
>
> int main()
> {
> int i;
> vertex *array;
> //create a priority_queue
> priority_queue<vertex *,vector<vertex *>,less<vector<vertex
> *>::value_type> >Q;
>
> //now can insert your elements of type vertex in pq
> for(i=0;i<9;++i)
> { array = new vertex;
> Q.push(array);}
> //now Q.top() will give the minimum value
> while(!Q.empty()){
> cout<<endl<<Q.top()->value;
> Q.pop();}
>
> cout<<endl<<endl;
>
> system("PAUSE");
> }
>
>
> But I got the result as..
>
> 9
> 8
> 7
> 6
> 5
> 4
> 3
> 1
> 2
>
> Press any key to continue . . .
>
> I couldnt explain this. How can I do the above this way (pointer way
> without array).
>
> On Jun 14, 5:15 am, "shaarang tyagi" <[EMAIL PROTECTED]> wrote:
> > you must do the following:
> >
> > class vertex
> > {
> > public:
> > vertex *parent;
> > int value;
> > vertex()
> > {
> > parent = NULL;
> > value = rand();
> > }
> > ~vertex();
> > }Array[10];
> >
> > bool operator < (const vertex& v1, const vertex& v2)
> > {
> > return (v1.value > v2.value);}
> >
> > vo
> id main()
> > {
> > //create a priority_queue
> >
> >
> priority_queue<vertex,vector<vertex>,less<vector<vertex>::value_type>
> >
> > > Q;
> >
> > //now can insert your elements of type vertex in pq
> > for(i=0;i<9;++i)
> > Q.push(Array[i]);
> > //now Q.top() will give the minimum value
> > cout<<Q.top().value;
> >
> > }
> > On Sat, Jun 14, 2008 at 3:40 PM, Pratyush <[EMAIL PROTECTED]>
> wrote:
> >
> > > I want to construct a min priority queue to hold class objects
> > > eg
> > > class vertex
> > > {
> > > public:
> > > vertex *parent;
> > > int value;
> > > vertex()
> > > {
> > > parent = NULL;
> > > value = rand();
> > > }
> > > ~vertex();
> > > }array[10];
> >
> > > priority_queue<vertex> Q;
> > > for(i=0;i<9;++i)Q.push(array[i]);
> >
> > > the min-heap is to be ordered by the "value" and Q.top() should return
> > > the vertex with min value ( like we require in prim's algorithm).
> > > Can anybody assist me how to create the priority_queue using STL in C+
> > > + and how is the comparator class and container is to be written for
> > > this.
> >
>
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