PAT 1009 Product of Polynomials

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<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define maxnum 100005

double a[] = {};
double b[] = {};
double c[maxnum] = {};

int main(){
    int n;cin >> n;
    int t;
    for(int i=;i < n;i++){
        int x;double y;
        cin >> x >> y;
        a[x] = y;
        if(!i)t = x;
    }
    int m;cin >> m;
    int start;
    for(int i=;i < m;i++){
        int x;double y;
        cin >> x >> y;
        b[x] = y;
        if(!i) start = x;
    }

    for(int i=;i < t+;i++){
        for(int j=;j < start+;j++){
            c[i+j] += a[i]*b[j];
        }
    }

    int cnt = ;
    for(int i=;i < maxnum;i++)if(c[i])cnt++;
    cout << cnt;

    for(int i=maxnum-;i>=;i--){
        if(c[i]) printf(" %d %.1lf",i,c[i]);
    }

    return ;
}

空间开的有点小炸，做了一下优化就好了，再一次理解错了提议，K<10，不一定就项系数<10，还好这题没出毒瘤卡边界数据，在超过1e5的地方直接放弃了。。