C++文件的输入输出

Question

录入考生学号和姓名，将考生信息写到文件中（e:\\1.txt)。
将学号为奇数的考生信息读出并打印在屏幕上。（不用写成图形界面，直接在DOS下打印出来就可以）。
注：将输出算法那写上注释。特别是关键函数

Answer 1

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

struct Student
{
int num;
char name[20];
}stu;

int main()
{

int i;
ofstream foutput;
foutput.open("e:\\1.txt");
if (foutput.fail())
{
cout<<"open file error!\n";
}
for (i = 0; i < 3; ++i)
{
cout<<"please input information:\n";
cin>>stu.num>>stu.name;
foutput<<stu.num<<" "<<stu.name<<endl;

}

foutput.close();
ifstream finput;
finput.open("e:\\1.txt");
if (finput.fail())
{
cout<<"open file error!\n";
}

while (finput>>stu.num>>stu.name)/////读入文件中的内容
{
if (stu.num%2)////判断学号是否为奇数
{
cout<<stu.num<<" "<<stu.name<<endl;
}
}

finput.close();
return 0;
}

Answer 2

#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

int main()
{
int n = 0;
cout << "学生人数: " << ends;
cin >> n;

ofstream of("Ko.txt");
if (!of)
{
cerr << "Con't not file error." << endl;
return -1;
}
int id;
string name;
for (int i = 0; i != n; ++i)
{
cout << "学号: " << ends;
cin >> id;
cout << "姓名: " << ends;
cin >> name;
of << id << ends;
of << name << endl;
}
of.close();

ifstream inf("Ko.txt");
if (!inf)
{
cerr << "Con't not file error." << endl;
return -1;
}

while (inf >> id >> name)
{
if (id % 2 != 0)
{
cout << id << ends
<< name << endl;
}
}
of.close();

return 0;
}

Answer 3

#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

int main()
{
int n = 0;
cout << "学生人数: " << ends;
cin >> n;

ofstream of("Ko.txt");
if (!of)
{
cerr << "Con't not file error." << endl;
return -1;
}
int id;
string name;
for (int i = 0; i != n; ++i)
{
cout << "学号: " << ends;
cin >> id;
cout << "姓名: " << ends;
cin >> name;
of << id << ends;
of << name << endl;
}
of.close();

ifstream inf("Ko.txt");
if (!inf)
{
cerr << "Con't not file error." << endl;
return -1;
}

while (inf >> id >> name)
{
if (id % 2 != 0)
{
cout << id << ends
<< name << endl;
}
}
of.close();

return 0;
}