C++ primer 练习4.22 答案

#include<iostream>
using namespace std;
#include<string>
class studentGrade          //学生类；
{
public:
	string finalgrade;   //成绩类别；
	int grade;            //成绩；
	studentGrade()
	{
		finalgrade = "UNKOWN";  
		grade = 0;
	}
	studentGrade(int grade1)
	{
		grade = grade1;
		if (rand() % 2 == 0)         //以二分之一的概率选用其中一种方式；
		{
			//三目运算符方式：
			finalgrade = grade1 < 60 ? "fail" : (grade1 < 75 ? "low pass" : (grade1 < 90 ? "pass" : "high pass"));
		}
		else
		{
			//if语句方式；
			if (grade1 < 60)
				finalgrade = "fail";
			else
			{
				if (grade1 < 75)
					finalgrade = "low pass";
				else
				{
					if (grade < 90)
						finalgrade = "pass";
					else
						finalgrade = "high pass";
				}
			}            //可见相比之下，if语句方式实在太烦；
		}
	}  
	~studentGrade()
	{
	}
};
int main()
{
	//测试用例；
	studentGrade s1(59), s2(62), s3(76), s4(92);
	cout << s1.grade << "  " << s1.finalgrade << endl;
	cout << s2.grade << "  " << s2.finalgrade << endl;
	cout << s3.grade << "  " << s3.finalgrade << endl;
	cout << s4.grade << "  " << s4.finalgrade << endl;
}