1009 Product of Polynomials (25)（25 分）

注意最后遍历不要包含maxn

#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 1e6 + 10;
double a[maxn], b[maxn], c[maxn];
int k;
void read(double a[])
{
    scanf("%d", &k);
    for (int i = 0; i < k; i++)
    {
        int exp;
        double coef;
        scanf("%d%lf", &exp, &coef);
        a[exp] = coef;
    }
}
int main()
{
    read(a);
    read(b);
    for (int i = 0; i < maxn; i++)
    {
        if (a[i])
        {
            for (int j = 0; j < maxn; j++)
            {
                if (b[j])
                {
                    c[i + j] += a[i] * b[j];
                }
            }
        }
    }
    int cnt = 0;
    for (int i = 0; i < maxn; i++)
    {
        if (c[i])cnt++;
    }
    printf("%d", cnt);
    for (int i = maxn-1; i >= 0; i--)
    {
        if (c[i])printf(" %d %.1f", i, c[i]);
    }
    return 0;
}