PAT (Advanced Level) Practise - 1009. Product of Polynomials (25)

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本文介绍了一种多项式相乘的算法实现，该算法通过读取两个多项式的系数和指数，计算并输出它们的乘积。输入为两个多项式的系数和指数信息，输出同样格式的乘积结果。

1009. Product of Polynomials (25)

时间限制

400 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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 N1 a_N1 N2 a_N2 ... NK a_NK, where K is the number of nonzero terms in the polynomial, Ni and a_Ni (i=1, 2, ..., K) are the exponents and coefficients, respectively. It is given that 1 <= K <= 10, 0 <= NK < ... < N2 < N1 <=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

多项式相乘。

#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <map>
using namespace std;
#define LL long long
const int maxn = 2200;
const int inf = 0x3f3f3f3f;
double a[maxn];
double b[maxn];
double ans[maxn];

int main()
{
    
    int n;cin>>n;
    for(int i=1;i<=n;i++){
        int k;
        double c;
        cin>>k>>c;
        a[k]=c;
    }
    cin>>n;
    for(int i=1;i<=n;i++){
        int k;
        double c;
        cin>>k>>c;
        b[k]=c;
    }
    for(int i=0;i<=1000;i++){
        for(int j=0;j<=1000;j++){
            ans[i+j]+=a[i]*b[j];
        }
    }
    int p=0;
    int num=0;
    for(int i=2000;i>=0;i--){
        if(ans[i]!=0){
            num++;
           
        }
    }
    printf("%d",num);
    for(int i=2000;i>=0;i--){
        if(ans[i]!=0){
            printf(" %d %.1lf",i,ans[i]);
        }
    }
    printf("\n");
    
}