实验7= =

#include<iostream>
#include<fstream>
using namespace std;
int main()
{
	ofstream out("test11.txt");
	if(!out)
	{
		cout<<"fail"<<endl;
		return 1;
	 } 
	 string a="已成功写入文件"; 
	 out<<a<<endl;
	 out.close();
	 return 0;
 } 

　　

#include<iostream>
#include<fstream>
#include<string>
using namespace std;
int main()
{
	ifstream in("H:\test11.txt");
	if(!in)
	{
		cout<<"fail"<<endl;
		return 1; 
	}
	string s;
	getline(in,s);
	cout<<s<<endl;
	return 0;
 } 

　　

#include<iostream>
#include<string>
#include<fstream>
using namespace std;
int main()
{
	fstream in("H:\test11.txt");
	if(!in)
	{
		cout<<"fail"<<endl;
		return 1;
	}
	in.clear();
	in.seekg(0,ios::end);
	string s;
	s="已成功添加字符";
	in<<s;
	in<<endl;
	in.close();
	return 0;
 } 

　　

#include<iostream>
#include<fstream>
#include<string.h> 
#include<stdlib.h>
#include<bits/stdc++.h>
using namespace std;
class C{
	public:
		int x;
		string xuehao;
		string name;
		string Class;
};
int main()
{
	int i=0;
	class C A[83];
	ifstream in("H:\list1.txt");
	ofstream out("roll.txt"); 
	if(!in)
	{
		cout<<"error"<<endl;
		return 1; 
	}
	while(in>>A[i].x>>A[i].xuehao>>A[i].name>>A[i].Class)
	{
		cout<<A[i].x<<"   "<<A[i].xuehao<<"   "<<A[i].name<<"   "<<A[i].Class<<"   "<<endl;	
		i++;
	}
	srand((unsigned)time(NULL));
	cout<<"下面随机抽取5位同学"<<endl;
	for(i=0 ;i<5 ;i++ )
	{
		int x=rand()%83;
		cout<<A[x].x<<"   "
			<<A[x].xuehao<<"   "
			<<A[x].name<<"   "
			<<A[x].Class<<"   "
			<<endl;
		out <<A[x].x<<"   "
			<<A[x].xuehao<<"   "
			<<A[x].name<<"   "
			<<A[x].Class<<"   "
			<<endl;
	}
//	cout<<"输入想操作的班级"<<endl;
	//string Class1;
	//cin>>Class1;
	//string ss="计科46(2)班";
//	if(strcmp(Class1.c_str(),ss.c_str())==0)
	//{
	//	for(i=0 ;i<83 ;i++ )
		//{
		//	if(strcmp((A[i].Class).c_str(),ss.c_str())==0)
			//	cout<<A[i].x<<"   "
				//	<<A[i].xuehao<<"   "
					//<<A[i].name<<"   "
					//<<A[i].Class<<"   "
					//<<endl;
	//	}
//	}
	in.close();
	out.close();
	return 0;
}

　　

 

#include<iostream>
#include<string.h>
#include<fstream>
using namespace std;
int main()
{
	char f[100];
	cin>>f;
	ifstream in(f);//很气，这里（）要地址= =， 
	if(!in)
	{
		cout<<"erroe"<<endl;
		return 1;
	} 
	string s;
	int duan=0;
	for(int i=0 ;;i++ )
	{
		if(getline(in,s))
		{
			duan++;
			cout<<s<<endl;
		}
		else break;
	}
	in.clear();//!!
	in.seekg(0);//!!这两行代码是返回文件的开头（in.seekg(xx,ios::beg)是返回到开头后第xxx位； 
	char ss;
	int z=0,zz=0,zzz;
	while (in>>ss)
	{
		zz++;
		if(ss>='A'&&ss<='z')
		z++;
	}
	in.clear();
	in.seekg(0);
	string sox;
	int sox_=0;
	while(in>>sox)
	sox_++;
	int shuru;
	cout<<"看文章的词数输入0"<<endl; 
	cout<<"看文章的字数输入1"<<endl; 
	cout<<"看标点一共多少输入2"<<endl; 
	cout<<"看文章段落输入3"<<endl; 
	while(cin>>shuru)
	{
		
		switch (shuru)
		{ 	
			case 0:
				cout<<"文章的词数为:"<<sox_<<endl; 
				break;
			case 1:
				cout<<"文章的字数为："<<z<<endl;
				break;
			case 2:
				cout<<"标点为："<<zz-z<<endl;
				break;
			case 3:
				cout<<"文章一共："<<duan<<"段"<<endl;
				break;
			default:
				break;		
		} 
		cout<<"看文章的词数输入0"<<endl; 
		cout<<"看文章的字数输入1"<<endl; 
		cout<<"看标点一共多少输入2"<<endl; 
		cout<<"看文章段落输入3"<<endl; 
		cout<<endl;	
	}	
	in.close();
	return 0;
}

　　

对于选作部分，还没做好= =，请谅解QWQ