【实验7】流类库与输入输出

11-3：

 1 #include <iostream>
 2 #include <fstream>
 3 
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     ofstream out("test1.txt");
 9     out << "已成功写入文件！" << endl;
10     out.close();
11     return 0;
12 }

截图略……

11-4

 1 #include <iostream>
 2 #include <fstream>
 3 #include <string>
 4 
 5 using namespace std;
 6 
 7 int main()
 8 {
 9     string x;
10     ifstream in("E:\\程序\\题目\\题目6\\11-3\\11-3\\test1.txt");
11     in >> x;
12     in.close();
13     cout << x << endl;
14     return 0;
15 }

截图略……

11-7

 1 #include <iostream>
 2 
 3 using namespace std;
 4 
 5 int main()
 6 {
 7     ios_base::fmtflags original_flags = cout.flags();        //保存当前参数设置
 8     cout << 812 << '|';
 9     cout.setf(ios_base::left, ios_base::adjustfield);        //左对齐 
10     cout.width(10);                                          //设置单次输出的域宽
11     cout << 813 << 815 << '/n';
12     cout.unsetf(ios_base::adjustfield);                      //清除左对齐
13     cout.precision(2);
14     cout.setf(ios_base::uppercase | ios_base::scientific);   //科学计数法
15     cout << 831.0;
16     cout.flags(original_flags);                              //恢复原先格式
17     return 0;
18 }

截图略……

应用练习1：

 1 #include <iostream>
 2 #include <cstdlib>
 3 #include <ctime>
 4 #include <fstream>
 5 #include <string>
 6 
 7 using namespace std;
 8 
 9 int main()
10 {
11     srand(time(NULL));
12     string x;
13     for (int i = 1; i <= 5; ++i)
14     {
15         int n = rand() % 16 + 1;
16         ifstream in("list.txt");
17         if (!in)
18         {
19             cerr << "open error!" << endl;
20             return 1;
21         }
22         for (int i = 1; i < n; i++)
23             in.ignore(1000, '\n');
24         getline(in, x);
25         in.close();
26         cout << x << endl;
27     }
28     return 0;
29 }

截图：

应用练习2：

 1 #include <iostream>
 2 #include <string>
 3 #include <fstream>
 4 
 5 using namespace std;
 6 
 7 int main()
 8 {
 9     string a;
10     cout << "Please enter the name of file: ";
11     cin >> a;
12     ifstream in(a);
13     if (!in)
14     {
15         cerr << "open error!" << endl;
16         return 1;
17     }
18     int number = 0, letter = 0, line = 0;
19     string x;
20     while (getline(in, x))
21     {
22         number += x.length();
23         bool flag = true;
24         for (int i = 0; i < x.length(); i++)
25         {
26             if (x[i] == ' '|| x[i] == '\n')
27             {
28                 if (flag == false)
29                 {
30                     letter++;
31                     flag = true;
32                 }
33             }
34             else if (flag == true)
35                 flag = false;
36         }
37         if (flag == false)
38             letter++;
39         line++;
40     }
41     in.close();
42     cout << "字符数：" << number << endl;
43     cout << "单词数：" << letter << endl;
44     cout << "行数：" << line << endl;
45     return 0;
46 }

截图：