1009 Product of Polynomials （25 分)

2019-03-08

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 N1 a**N1 N2 a**N2 … N**K aNK

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

1 2	2 1 2.4 0 3.2 2 2 1.5 1 0.5

Sample Output:

1	3 3 3.6 2 6.0 1 1.6

作者: CHEN, Yue

单位: 浙江大学

时间限制: 400 ms

内存限制: 64 MB

代码长度限制: 16 KB

题目大意

输入指数和系数代表两个多项式，要求输出相乘之后的结果

分析

使用结构体po代表一项，利用vector存储po代表一个多项式。先缓存第一个，然后在线处理第二个，将每一项相乘的结果存入res，合并指数相同的项即可。注意系数为0的项不输出。

代码

#include <iostream>
#include <vector>
#include <algorithm>
#include <deque>
#include <map>
#include <cstring>
using namespace std;
struct po{
    int n;
    double an;

    po(int n, double an) : n(n), an(an) {}
};

bool cmp(po p1,po p2){
    if(p1.n>p2.n)
        return true;
    return false;
}
int main() {
    int k;
    int n,c=0;
    double an;
    cin>>k;
    vector<po> temp;
    vector<po> res;
    for(int i=0;i<k;i++){
        cin>>n>>an;
        temp.push_back(po(n,an));
    }
    cin>>k;
    for(int i=0;i<k;i++){
        cin>>n>>an;
        for(auto it=temp.begin();it!=temp.end();it++){
            int f=0;
            po p(n+it->n,an*it->an);
            for(auto itt=res.begin();itt!=res.end();itt++){
                if(itt->n==p.n) {
                    itt->an += p.an;
                    f=1;
                }
            }
            if(f)
                continue;
            res.push_back(p);
        }
    }
    sort(res.begin(),res.end(),cmp);
    for(po p:res)
    {
        if(p.an!=0)
            c++;
    }
    cout<<c;
    for(po p:res){
        if(p.an!=0)
       // cout<<" "<<p.n<<" "<<p.an;
        printf(" %d %.1f",p.n,p.an);
    }

    return 0;
}