A+B for Polynomials (25 分)

题目描述：
This time, you are supposed to find A+B where A and B are two polynomials.

Input

Each input file contains one test case. Each case occupies 2 lines, and each line contains the information of a polynomial: $K N_1$ $a_{N1}$ $N_2$ $a_{N2} ...$ $N_K$ $a_{NK}$ , where K is the number of nonzero terms in the polynomial, $N_i$ 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

For each test case, you should output the sum 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 to 1 decimal place.

Sample Input
2 1 2.4 0 3.2
2 2 1.5 1 0.5
Sample Output
3 2 1.5 1 2.9 0 3.2

注意点：

coefficients可以是负数
系数为0不进行输出
如果size为0，直接输出0
最后没有空格

#include<iostream>
#include<map>
#include<vector>

using namespace std;

map<int, float> poly1;
int main() {
    for (int i = 0; i < 2; ++i)
    {
        int n1;
        scanf("%d", &n1);
        for (int i = 0; i < n1; ++i)
        {
            int exp;
            float cof;
            scanf("%d%f", &exp, &cof);
            poly1[exp] += cof;
        }
    }
    vector<pair<int, float> > res;
    for(map<int, float>::reverse_iterator it = poly1.rbegin(); it != poly1.rend(); it++) {
        if(it->second != 0) // 两个系数和为0的得过滤掉
            res.push_back(make_pair(it->first, it->second));
    }

    printf("%lu", res.size());
    for (int i = 0; i < res.size(); ++i)
    {
        printf(" %d %.1f", res[i].first, res[i].second);
    }
    return 0;
}