c++面向对象程序设计

//EXERCISE 2.1
//Write a program that reads integers from the standard input until the end of file and then prints the largest and the smallest values  

#include<iostream>
#include<fstream>
using namespace std;
int main()
 {
     int n,max=0,min=0;
     cout << "input the biggest number:"<<endl;
     cin >> n; 
     ifstream fin;
     fin.open("in.txt");
     int *a = new int[n];
      if(!fin)
     {
         cout <<"failure"<<endl;
         exit(0);
         
     }
     for(int i =0;i<n;i++)
     {
         fin >> a[i];
         if(a[max]<a[i])
         max =i;
         if(a[min]>a[i])
         min = i;
     }
     fin.close();
     cout << "the max is" << a[max]<<endl;
      cout << "the min is" << a[min]<<endl;
      delete[] a;
      return 0;
 }
 
 
 

　　

 2.2 Write a program that echoes the standard input to the standard output,except that each tab is replaced by the approriate name of spaces.Assume that tabs are set evey 8 columns,unless the user specifies a different tab setting on the command line.(讲真。。。题目我没看懂)

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
	int a,b,c;
	cin >>a>>b>>c;
	cout <<setw(8) << a<<endl;
	cout <<setw(8) << b<<endl;
	cout <<setw(8) << c<<endl;
	return 0;
}

　　2.3 write a function db1that takes an int argument and multiplies it by 2.Pass the argument by reference.

#include<iostream>
using namespace std;
void db1(int&);
int main()
{
	int x = 6;
	db1(x);
	cout << x <<end
	return 0;
	
}

void db1(int& ref)
{
	ref = 2 * ref;
}