A1009 Product of Polynomials (25分)

This time, you are supposed to find A×B where A and B are two polynomials.

Input Specification:

Each input file contains one test case. Each case occupies 2 lines, and each line contains the information of a polynomial:

K N​1​​ a​N​1​​​​ N​2​​ a​N​2​​​​ ... N​K​​ a​N​K​​​​

where K is the number of nonzero terms in the polynomial, N​i​​ and a​N​i​​​​ (i=1,2,⋯,K) are the exponents and coefficients, respectively. It is given that 1≤K≤10, 0≤N​K​​<⋯<N​2​​<N​1​​≤1000.

Output Specification:

For each test case you should output the product of A and B in one line, with the same format as the input. Notice that there must be NO extra space at the end of each line. Please be accurate up to 1 decimal place.

Sample Input:

2 1 2.4 0 3.2
2 2 1.5 1 0.5

Sample Output:

3 3 3.6 2 6.0 1 1.6

 Solution:

#include <cstdio>

struct Poly {
    int exp;
    double cof;
}p[1001];

double ans[2001] = {0};

int main() {
    int n1, n2, exp, cnt = 0;
    double cof;
    scanf("%d", &n1);
    for (int i = 0; i < n1; i++) {
        scanf("%d%lf", &p[i].exp, &p[i].cof);
    }
    scanf("%d", &n2);
    for (int i = 0; i < n2; i++) {
        scanf("%d%lf", &exp, &cof);
        for (int i = 0; i < n1; i++) {
            ans[p[i].exp+exp] += p[i].cof*cof;
        }
    }
    for (int i = 0; i < 2001; i++) {
        if (ans[i] != 0) {
            cnt++;
        }
    }
    printf("%d", cnt);
    for (int i = 2000; i >= 0; i--) {
        if (ans[i] != 0) {
            printf(" %d %.1lf", i, ans[i]);
        }
    }
    return 0;
}