1009 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​​​​ (,) are the exponents and coefficients, respectively. It is given that 1, 0.

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

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
double a[1001] = { 0.0 }, b[1001] = { 0.0 }, c[2001] = { 0.0 };



int main() {
    int k;
    cin >> k;
    int i, j;
    while (k--) {
        cin >> i;
        cin >> a[i];
    }
    cin >> k;
    while (k--) {
        cin >> i;
        cin >> b[i];
    }
    
    for (i = 0; i <= 1000; i++) {
        for (j = 0; j <= 1000; j++) {
            c[i+j] += a[i] * b[j];
        }
    }
    int cnt = 0;
    char str[1000] = "", str1[100];
    for (i = 2000; i >= 0; i--) {
        if (c[i] != 0.0) {
            sprintf(str1, " %d %0.1lf", i, c[i]);
            strcat(str, str1);
            cnt++;
        }
    }
    cout << cnt << str;

}