在我的程序中的这一点上，我每次编写一个随机数时，数组中该数字的内容被写入文本文件。代码：
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
#include <time.h>
#include "inFrench.h"
using namespace std;
class student
{
int m_studentNumber;
public:
string nameFirst;
string nameLast;
string nameFull;
int getStudentNumber() { return m_studentNumber; }
void setStudentNumber(int studentNumber) { m_studentNumber = studentNumber; }
};
ostream& operator<<(ostream& os, const student& s)
{
return os << s.nameFirst << ' ' << s.nameLast;
}
student typeName()
{
student bar;
cout << "Type in a student's first name: ";
cin >> bar.nameFirst;
cout << "Type in that student's last name: ";
cin >> bar.nameLast;
bar.nameFull = bar.nameFirst + " " + bar.nameLast;
return bar;
}
void displayStudents(student listOfStudents[50], int studentHeadCount)
{
for (int i = 0; i < studentHeadCount; i++)
{
cout << listOfStudents[i].nameFull << endl;
cout << listOfStudents[i].getStudentNumber() << endl;
cout << "\n";
}
}
void generateGroups(int numberOfGroups, int maxStudents, int studentsPerGroup, int remainder, student theStudents[], int studentsBeenAssigned, ofstream studentGroups)
{
int k;
numberOfGroups = maxStudents / studentsPerGroup;
cout << numberOfGroups << endl;
srand(time(NULL));
studentGroups.open("studentGroups.txt");
while (studentsBeenAssigned < maxStudents && studentsBeenAssigned < maxStudents - remainder)
{
for (int j = 0; j < maxStudents - remainder; j++)
{
k = rand() % maxStudents;
cout << theStudents[k].nameFull << endl;
studentGroups << theStudents[k].nameFull << endl;
studentsBeenAssigned++;
if (studentsBeenAssigned == studentsPerGroup)
{
cout << "\n";
studentGroups << theStudents[k].nameFull << endl;
studentsBeenAssigned = 0;
}
}
}
if (remainder < studentsPerGroup && remainder > 0)
{
for (int l = 0; l < remainder; l++)
{
cout << theStudents[k].nameFull << endl;
}
}
}
void languageChoices()
{
cout << "Select your language from the following:\n";
cout << "a) English\n";
cout << "b) French\n";
cout << "\n";
}
void options()
{
cout << "Select what you want to do:\n";
cout << "1) Exit application\n";
cout << "2) Enter a Student\n";
cout << "3) Display Students\n";
cout << "4) Display Groups\n";
cout << "5) Output groups as text file\n";
cout << "6) Reset number of students in class\n";
cout << "7) Reset number of students per group\n";
cout << "\n";
}
int main()
{
char selectedLanguage;
languageChoices();
cin >> selectedLanguage;
switch (selectedLanguage)
{
case 'a':
{
student allStudents[50]; // Having 50 students alone is ridiculous!
bool endProg = 0;
int maxStudents;
int studentsPerGroup;
int optionSelect;
int studentHeadCount = 0;
int remainder = 0;
int numberOfGroups = 0;
int studentsBeenAssigned = 0;
ofstream studentGroups;
cout << "GroupPicker 1.0\n";
cout << "Note: This version of the program is intended for purposes of education only, "
<< "specifically for teacher use in a classroom.\n\n";
cout << "How many students are in the class?\n" << "(Note: You cannot have more than 50 in this program)\n";
cin >> maxStudents;
if (maxStudents > 50)
{
cerr << "Too many students!\n" << "Exiting program...\n";
system("PAUSE");
exit(1);
}
if (maxStudents >= 35 && maxStudents <= 50)
{
cout << maxStudents << " students? You are a pro!\n";
}
cout << "How many students per group?\n";
cin >> studentsPerGroup;
if (studentsPerGroup >= maxStudents || studentsPerGroup <= 1)
{
cerr << "You're kidding, right?\n" << "Exiting program...\n";
system("PAUSE");
exit(1);
}
while (endProg == 0) {
options();
cin >> optionSelect;
switch (optionSelect) {
case 1:
endProg = 1;
break;
case 2:
{
if (studentHeadCount == maxStudents)
{
cerr << "You can't enter more than " << maxStudents << " students\n";
}
else
{
allStudents[studentHeadCount] = typeName();
allStudents[studentHeadCount].setStudentNumber(studentHeadCount);
cout << "Student (" << allStudents[studentHeadCount].nameFull << ") entered.\n";
cout << "\n";
studentHeadCount++;
}
break;
}
case 3:
cout << "Current list of students:\n\n";
displayStudents(allStudents, studentHeadCount);
break;
case 4:
{
if (studentHeadCount < studentsPerGroup || studentHeadCount < maxStudents)
{
cerr << "Invalid group parameters.\n" << "Returning to main menu...\n\n";
break;
}
else
{
cout << "Here are the groups:\n\n";
studentGroups.open("studentGroups.txt");
generateGroups(numberOfGroups, maxStudents, studentsPerGroup, remainder, allStudents, studentsBeenAssigned, studentGroups);
}
break;
}
case 5:
{
cout << "Saving groups to file...\n";
studentGroups.close();
break;
}
case 6:
{
cout << "How many students are in the class?\n" << "(Note: You cannot have more than 50 in this program)\n";
cin >> maxStudents;
if (maxStudents > 50)
{
cerr << "Too many students!\n" << "Try again...\n";
}
if (maxStudents >= 35 && maxStudents <= 50)
{
cout << maxStudents << " students? You are a pro!\n";
}
break;
}
case 7:
{
cout << "How many students per group?\n";
cin >> studentsPerGroup;
if (studentsPerGroup >= maxStudents || studentsPerGroup <= 1)
{
cerr << "You're kidding, right?\n" << "Try again...\n";
}
break;
}
}
}
break;
}
case 'b':
{
mainInFrench();
}
}
}
编译时，我收到以下错误：
error C2248: 'std::basic_ofstream<_Elem,_Traits>::basic_ofstream' : cannot access private member declared in class 'std::basic_ofstream<_Elem,_Traits>'
IntelliSense: "std::basic_ofstream<_Elem, _Traits>::basic_ofstream(const std::basic_ofstream<_Elem, _Traits>::_Myt &_Right) [with _Elem=char, _Traits=std::char_traits<char>]" (declared at line 1034 of "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\fstream") is inaccessible
如何解决这些问题（第181行）并确保不会多次生成任何数字？
答案 0 :(得分：3)
您将按值传递给generateGroups()函数，这会导致复制构造函数调用。标准流无法复制。
至于你问题的第二部分，你不能指望PRNG总是返回唯一数字，更不用说当你用模数限制范围时。您需要编写更多代码，以检查您之前已经生成的数字是否已经生成，或者换句话说，某些学生已被分配。
答案 1 :(得分：3)
std::ofstream无法复制。看起来你需要一个参考：
void generateGroups(int numberOfGroups, int maxStudents,
int studentsPerGroup, int remainder,
student theStudents[], int studentsBeenAssigned,
ofstream& studentGroups)
{// ^
答案 2 :(得分：1)
rand（）使用的种子在大多数实现中不会重复直到2 ^ 32个循环或更多，但是（种子＆gt;＆gt; xx）％n将至少每n个循环重复一次，如果n不相对则更频繁地重复对rand（）使用的linear congruential generator使用的数字进行素数处理。
您可以创建一个包含n个字节的数组，并使用它们来跟踪是否存在重复。