题目
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 N1 aN1 N2 aN2 … NK aNK, where K is the number of nonzero terms in the polynomial, Ni and aNi (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
大意：求多项式加法，精确到小数点后1位。
思路
用map存储指数和系数的映射关系，如果出现系数为0，则从map中删去。
map是自动排序的，只需后序遍历输出即可。
注意题目要求精确到小数点后1位，加上控制输出即可。
代码
#include <iostream>
#include <iomanip>
#include <map>
using namespace std;int main(){map<int, float> coefMap;for (int i=0; i<2; i++){int k;cin >> k;for (int j=0; j<k; j++){int exp;float coef;cin >> exp >> coef;coefMap[exp] += coef;if (coefMap[exp]==0){coefMap.erase(exp);}}}cout << coefMap.size();for (auto it=coefMap.rbegin(); it!=coefMap.rend(); ++it){cout << " " << it->first << " " << fixed << setprecision(1) << it->second;}cout << endl;return 0;
}