实验七

#include<iostream>
using namespace std;
int main()
{
    ios_base::fmtflags original_flags=cout.flags();// 保存一些参数的设置 
    cout<<812<<'|';
    cout.setf(ios_base::left,ios_base::adjustfield);// 对齐方式变为左对齐 
    cout.width(10);// 输出宽度变成10 
    cout<<813<<815<<'\n';
    cout.unsetf(ios_base::adjustfield);// 去除现在的对齐方式 
    cout.precision(2);
    cout.setf(ios_base::uppercase|ios_base::scientific);// 使用科学计数法 
    cout<<831.0;
    cout.flags(original_flags);// 恢复cout原有的设置 
    return 0;
 } 

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

int main()
{ ofstream outfile;
outfile.open("test1.txt");
outfile<<"111111"<<endl;
outfile.close();
ifstream putfile;
putfile.open("test1.txt");
char ch;
while(putfile.get(ch))
    cout<<ch;

putfile.close();
return 0;

}

第 二三题

 

#include <bits/stdc++.h>
using namespace std;

struct classmates {     
    int number;         
    long long id;       
    string name;        
    string classname;   
};

int main()
{
    vector <classmates> temp;
    int all = 0;    
    
    ifstream file("list.txt");
    if (!file) {
        cout << "open file error!" << endl;
        return 1;
    }
    ;
    
    classmates x;
    while (file >> x.number >> x.id >> x.name >> x.classname) {
        temp.push_back(x);
     */
        ++all;
    }
    
    file.close();
    
    ofstream outfile("roll.txt");
    if(!outfile){
        cout<<"creat outfile failed"<<endl;
        return 1;
    }
    
    struct timeb timeSeed;
    ftime(&timeSeed);
    srand(timeSeed.time * 1000 + timeSeed.millitm);  
    double result[5];
    for (int j = 0; j < 5; j++) {
        result[j] = rand() % all;
       
        cout << temp[result[j]].number << "  " << temp[result[j]].id << "  "
             << temp[result[j]].name << "  " << temp[result[j]].classname << endl;
        outfile << temp[result[j]].number << "  " << temp[result[j]].id << "  "
                << temp[result[j]].name << "  " << temp[result[j]].classname << endl;
    }
    outfile.close();
    return 0;
}