程序代码：

#include <queue>
#include <iostream>
using namespace std;

struct foo
{
    int x, y, z;

    foo( int x, int y, int z ) : x(x), y(y), z(z)
    {
    }
};

struct foo_comp_z
{
    bool operator()( const foo& lhs, const foo& rhs ) const
    {
        return lhs.z < rhs.z;
    }
};

int main( void )
{
    std::priority_queue<foo,std::vector<foo>,foo_comp_z> q;
    q.push( foo(0,0,2) );
    q.push( foo(0,0,1) );
    q.push( foo(0,0,3) );

    for( ; !q.empty(); q.pop() )
        cout << q.top().z << endl;

    return 0;
}