Skip to content

Product of Polynomials

题目链接1009 Product of Polynomials (25 分)

题干大意

多项式乘法实现，常规

思路

一个向量存第一个多项式，后面一个多项式边读边计算即可

AC代码

C++
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
#include <iomanip>
#include <iostream>
#include <vector>
using namespace std;

void calc(vector<double>& res, const vector<int>& index, const vector<double>& value, const int a, const double b)
{
    for (auto it = index.begin(); it != index.end(); ++it)
        res[a + *it] += b * value[it - index.begin()];
}

int main()
{
    int    k, a;
    double b;

    vector<int>    index;
    vector<double> value, res(2001);

    cin >> k;
    for (auto i = 0; i < k; ++i) {
        cin >> a >> b;
        index.push_back(a);
        value.push_back(b);
    }

    cin >> k;
    for (auto i = 0; i < k; ++i) {
        cin >> a >> b;
        calc(res, index, value, a, b);
    }

    int count = 0;
    for (auto& p : res)
        if (p != 0.0)
            ++count;
    cout << count;
    for (auto it = res.end() - 1; it >= res.begin(); --it)
        if (*it != 0.0)
            cout << " " << it - res.begin() << " " << setiosflags(ios::fixed) << setprecision(1) << *it;
    return 0;
}