1009. Product of Polynomials (25)

时间限制

400 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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 ... NK a_NK, where K is the number of nonzero terms in the polynomial, Ni 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 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

2 1 2.4 0 3.22 2 1.5 1 0.5

Sample Output

3 3 3.6 2 6.0 1 1.6

这题确实不难，思路也很简单，类似前面求多项式的和。但是题意一定要理解清楚，想要过所有的测试用例不容易啊，并且每个测试用例都是五分，如果真的是考试，一点小差错丢掉五分很不值得。下面是我的代码，用的思路是用浮点型数组存多项式，数组下标是指数，对应的值的系数。里面有很多要注意的小点，在程序中有标出：

#include<vector>#include <sstream>#include<cmath>#include<iomanip>#include<iostream>#include <ctype.h>#include <stdlib.h>#include <algorithm>using namespace std;int main(){int n, m;float numa[1001] = {0.0};//存放A中的各项信息，下标是指数，数组的值是对应的系数float numb[1001] = {0.0};float product[2005] = {0.0};//存入乘积的结果cin >> n;for (int i = 0; i < n; i++){int temp;cin >> temp;cin >> numa[temp];}cin >> m;for (int i = 0; i < m; i++){int temp;cin >> temp;cin >> numb[temp];}for (int i = 0; i <1001; i++)//i，j的取值尤其注意，一开始没考虑周全，导致两个测试用例出错{ for (int j = 0; j <1001; j++){float coeff = numa[i] * numb[j];int exp = i + j;product[exp] = product[exp]+ coeff;//注意这里的逻辑不要写错了}}int count = 0;float t = 0.05;for (int i = 0; i < 2005; i++)//特别注意取值范围{if (abs(product[i])>=t)//这里要特别注意，四舍五入后为0的项，也不能显示，并且要加绝对值才能通过最后一个测试用例，但是我其实不是很明白，他们都是大于0的数，为何要加绝对值，但是不加真的就是通不过第一个测试用例，减5分count++;}cout << count;for (int i = 2004; i >=0; i--)//特别注意取值范围{if (abs(product[i])>= t){cout << " " << i << " " << setiosflags(ios::fixed) << setprecision(1) << product[i];}}return 0;}