第十六週C++【任務二】學生成績排序

【任務2】學生成績排序
文件score.dat 中保存的是100 名學生的姓名和C++課、高數和英語成績。
（1）定義學生類，其中包含姓名、C++課、高數和英語成績及總分、均分數據成員，成員函數根據
需要確定。
（2）讀入這名學生的成績，用對象數組進行存儲。
（3）求出各科和總分的最高分。
（4）請按總分的降序（高成績在前，低成績在後）排序
（5）在屏幕上顯示各科及總分的最高分，排序後的成績單（包括總分）保存到文件odered_score.dat
中

 

#include<iostream> 
#include <string>
using namespace std;
#include<fstream>
class Student
{
public:
	double get_total();
	double get_average();
	void get_name(string name);
	void get_c_score(double c_score);	
	void get_m_score(double m_score);
	void get_e_score(double e_score);
	friend void input(Student *stu) ;
	friend void output(Student *stu);
	friend void output_max(Student *stu);
	friend void paixu(Student *stu);
private:
	string name;
	double c_score;
	double m_score;
	double e_score;
	double total;
	double average;
};

double Student::get_total()
{
	(this->total) = (this->c_score + this->e_score + this->m_score);
	return (this->total);
}

double Student::get_average()
{
	(this->average) = (this->c_score + this->e_score + this->m_score)/3;
	return (this->average);
}
void Student::get_name(string name)
{
	this->name = name;
}
void Student::get_c_score(double c_score)
{
	this->c_score = c_score;
}
void Student::get_m_score(double m_score)
{
	this->m_score = m_score;
}
void Student::get_e_score(double e_score)
{
	this->e_score = e_score;
}
void input(Student stu[])
{
	string name;
	int i;
	double c_score;
	double m_score;
	double e_score;
	ifstream inFile("score.dat",ios::in);
		if(!inFile)
		{
			cerr<<"open error!"<<endl;
			exit(1);
		}
		for( i=0;i<100;++i)
		{
			inFile>>name;
			stu[i].get_name( name);

			inFile>>c_score;
			stu[i].get_c_score( c_score);
			inFile>>e_score;
			stu[i].get_e_score( e_score);

			inFile>>m_score;
			stu[i].get_m_score( m_score);
		}
		inFile.close();
}

void output(Student *stu)
{
	ofstream writeFile("odered_score.dat",ios::out);
		if(!writeFile)
		{
			cerr<<"open error!"<<endl;
			exit(1);
		}
		for(int i=0;i<100;++i)
		{
			writeFile<<stu[i].name;
			cout<<stu[i].name<<" ";
			writeFile<<stu[i].c_score;
			cout<<stu[i].c_score<<" ";
			writeFile<<stu[i].e_score;
			cout<<stu[i].e_score<<" ";
			writeFile<<stu[i].m_score;
			cout<<stu[i].m_score<<" ";
			writeFile<<stu[i].average;
			cout<<stu[i].average<<" ";
			writeFile<<stu[i].total;
			cout<<stu[i].total<<" ";
			cout<<endl;
		}
		writeFile.close();

}
void output_max(Student *stu)
{
	double max1,max2,max3,max4;
	max1=stu[0].c_score;
	max2=stu[0].m_score;
	max3=stu[0].e_score;
	max4=stu[0].get_total();
	for(int i=0;i<100;++i)
	{
		if(stu[i].c_score>max1)
		{
			max1=stu[i].c_score;
		}
		
		if(stu[i].m_score>max2)
		{
			max2=stu[i].m_score;
		}
		
		if(stu[i].e_score>max3)
		{
			max3=stu[i].e_score;
		}
	
		if(stu[i].get_total()>max4)
		{
			max4=stu[i].get_total();
		}
		
	}
	cout<<max1<<endl;
	cout<<max2<<endl;
	cout<<max3<<endl;
	cout<<max4<<endl;

}

	void paixu(Student *stu)
	{
		
		Student t;
		for( int i=0;i<100;++i)
		{
			stu[i].get_total();
			stu[i].get_average();
		}
		for(int i=0;i<99;++i)
			for(int j=0;j<99-i;++j)
			{
				if(stu[i].total<stu[i+1].total)
				{
					t=stu[i];
					stu[i]=stu[i+1];
					stu[i+1]=t;
				}
			}
	}
int main()
{	
	Student stu[100]; 
    input(stu);
	output_max(stu);
	paixu(stu);
	output(stu);
    cout<<endl;  
	system("PAUSE");  
    return 0;  


}

 

 

積累經驗：文件的輸入輸出是有一定套路的，掌握其方法，萬變不離其中。

writeFile<<stu[i].name;這裏只是將數據向磁盤文件輸出，所以在屏幕上看不見輸出結果，要想輸出，就加上cout<<stu[i].name<<" ";

這一點與電子詞典不同。而且在讀入數據時，此處涉及到了傳參。