Question

我要做的是在多个文本文件中生成随机数，这是我当前的代码：

// Write files
        string file_name_write = "2016\\Sem2\\Timetable_list\\Timetable" + s->Get_subid() + ".txt";
        ofstream fo (file_name_write.c_str()); // E.g: Timetable_list\TimetableICT1.1.txt
        fo << "Subject ID: " << s->Get_subid() << endl;
        fo << "Subject name: " << s->Get_name() << endl;
        fo << "Lecturer: " << s->lecturer << endl;
        fo << "Venue: " << s->venue << endl;
        fo << "Time: " << s->time << endl << endl; 
        fo << "List of students for this subject:" << endl;
        fo << "Order    ID  Name        DOB     Address     E.Year  Major   Midterm Final   Total" << endl;
        int n = s->number_of_students; 
        Student *temp_stu;
        srand(time(NULL));
        for (int i=0; i<n; i++) 
        {
            int random_mid;
            int random_final;
            random_mid = (rand() % 20) + 1;
            random_final = (rand() % 20) + 1;
            temp_stu = lstu.Find_Student (s->stu_id[i]);
            fo << i+1 << "  " << temp_stu->Get_pid() << "   " << temp_stu->Get_fname() << " "
               << temp_stu->Get_dob() << "  " << temp_stu->Get_addr() << "      "
               << temp_stu->Get_ent_year() << " " << temp_stu->Get_major() << " " << random_mid 
               << " " << random_final << endl;
        }
        fo.close();
        s = s -> next;

我遇到的问题是我的文本文件中的随机数列表完全相同。例如，我的每个文件都生成相同的数字：

Midterm Final
  14     16
  12     5
  5      1
  12     15
  19     18

我希望我的程序在每个文本文件中生成不同的数字列表，任何想法我该怎么做？谢谢。

Answer 1

调用时间（NULL）将返回秒，因此您的代码会在同一秒内使用相同的种子重新初始化PRNG。举个例子：

srand (33); // initialize with a fixed seed = 33.
printf ("random number: %d, %d, %d\n", rand()%100, rand()%100, rand()%100);
// > random number: 41, 15, 22

srand (33); // re-initialize with the same seed = 33.
printf ("random number: %d, %d, %d\n", rand()%100, rand()%100, rand()%100);
// > random number: 41, 15, 22

您必须在应用程序启动时初始化PRNG一次：

int main () {
    srand(time(NULL));
    ... // other code

在多个文本文件中生成随机数

1 个答案: