1009 Product of Polynomials (25分)

#include <iostream>
#include <vector>
using namespace std;
struct node
{
    int n;
    double a;//n为次数，a为系数
};
int main()
{
    vector<node> v1,v2;
    int k;
    cin >> k;
    struct node* p =new struct node;
    while(k--)
    {
        cin >> p->n >> p->a;
        v1.push_back(*p);
    }
    vector<node>::iterator it1;
    vector<double> v3(2002);
    cin >> k;
    while(k--)
    {
        cin >> p->n >> p->a;
        for(it1 = v1.begin(); it1 != v1.end(); ++it1)
            v3[p->n + it1->n] += p->a * it1->a;    
    }
    int cnt = 0;
    for(int i = 0; i<=2001; ++i)
    {
        if(v3[i] != 0)
            ++cnt;
    }
    printf("%d",cnt);
    for(int i = 2001; i >= 0; --i)
    {
        if(v3[i] != 0)
            printf(" %d %.1f",i,v3[i]);
    }
    return 0;
}