HDU1202 无语题

#include<iostream>
#include<iomanip>
using namespace std;

double judge_score(int tem)  //分数对应的点数，题目给出的只是整数，所以调用时要强制类型转化
{
	if(tem>=90 && tem<=100)
		return 4.0;
	else if(tem>=80 && tem<=89)
		return 3.0;
	else if(tem>=70 && tem<=79)
		return 2.0;
	else if(tem>=60 && tem<=69)
		return 1.0;
	return 0.0;
}

int main()
{
	int t,i;
	double credit,score;

	while(cin>>t)
	{
		double all_score=0.0,all_credit=0.0;
		for(i=0;i<t;i++)
		{
			cin>>credit>>score;
			
			if(score!=-1)  //分数为-1，不计算
			{
				all_score+=judge_score(int(score))*credit; //分数的强制类型转化，应该很重要，没做这个，结果WA了8次
				all_credit+=credit;
			}
		}

		if(all_credit==0.0 || all_score==0.0)  //GPA不存在
		{
			cout<<-1<<endl;
			continue;
		}

		double GPA=all_score*1.0/all_credit;
		cout<<setiosflags(ios::fixed)<<setprecision(2)<<GPA<<endl;
	}
	return 0;
}