9-5.cpp

Accelerated C++ 课后练习题 本人自己完成、可供参考

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<iomanip>
class Student_info
{
public:
	Student_info();
	Student_info(std::istream&);
	std::string name() const
	{
		return n;
	}
	double average()
	{
		return (midterm+final)/2;
	}
	std::istream& read(std::istream&);
private:
	std::string n;
	double midterm,final;
};

Student_info::Student_info():midterm(0),final(0)
{
}
std::istream& Student_info::read(std::istream& in)
{
	in>>n>>midterm>>final;
	return in;
}
Student_info::Student_info(std::istream& is)
{
	read(is);
}
bool compare(const Student_info& a,const Student_info& b)
{
	return a.name()<b.name();
}

char estimate(double a)
{
	return a>60?'F':'P';
}
int main()
{
	std::vector<Student_info> students;
	Student_info record;
	std::string::size_type maxlen=0;
	while(record.read(std::cin))
	{
		maxlen=std::_MAX(maxlen,record.name().size());
		students.push_back(record);
	}
	std::sort(students.begin(),students.end(),compare);

	std::streamsize prec=std::cout.precision();
	for(std::vector<Student_info>::size_type i=0;
			i<students.size();++i)
				std::cout<<students[i].name()<<std::string(maxlen-students[i].name().size()+4,' ')
		         <<std::setprecision(4)<<estimate(students[i].average())
				 <<std::setprecision(prec)<<std::endl;

	return 0;
}