PAT 1009. Product of Polynomials (25)

#include<iostream>#include<cstdio>#include<vector>using namespace std;float num[2001] = { 0 };int cnt = 0;int main(){vector<int> exp1;vector<float> coef1;int k; cin >> k;//exp1.resize(k); 加上这两句答案会错误，为何?//coef1.resize(k);int len1 = k;for (int i = 0; i < k; i++){int exp; float coef;cin >> exp >> coef;exp1.push_back(exp);coef1.push_back(coef);}cin >> k;for (int i = 0; i < k; i++){int exp; float coef;cin >> exp >> coef;for (int j = 0; j < len1; j++){num[exp + exp1[j]] += coef* coef1[j];//核心就是这一句}}for (int i = 0; i < 2001; i++){if (num[i] != 0)cnt++;}cout << cnt;for (int i = 2000; i >= 0; i--){if (num[i] != 0){cout << " " << i;printf(" %.1f", num[i]);}}}