Cannot get the random string - c++

Question

I am using C++ to create an app for Random Questions. But I don't think that works (due to my bad logics). What I am trying is this:
class English {
public:
string get_questions (int number) {
if (number == 1) {
// Chapter 1
string questions[10] = {
"In what way is man considere to be a lower species when compared to animals, in general?",
"What specific triats of character make man the lowest animal in Mark Twain's views?",
"What aspects of human nature are pointed when man is compared with the anaconda, bees, roosters, cats.",
"What specific traits of character make man the lowest animal in Mark Twain's views?",
"Discuss the Importance of the experiments conducted by the Mark Twain.",
"Can people improve themselves and remove this label in thismillennium?",
"What are the traits due to which man cannot claim to have reached the meanest of the Higher Animals?",
"\"The damned Human Race\" was written in 1900, is it valid today?",
"Do you think Mark Twain was accurate while comparing Human nature to that of the birds, insects and other animals?",
"Why did Mark Twain rejected Darwin's theory, what were his conclusions in this regard?"
};
string result = questions[rand() % 9 + 0] + "\n";
return result;
}
}
};
And the code that I am using is something like this:
cout << English().get_questions(chapter);
Although I have more lines, but they are just simple cout and cin to get the chapter and subject values. They won't be a trouble for this.
The main issue here is that everytime I am done writing the code, when I compile and execute it, same question is provided as a result everytime. Forexample, for the current random logic, I get this question:
Can people improve themselves and remove this label in this millennium?
Whenever I change the logic, I get a new result but similar in every condition (code execution for that particular logic)! Where as what I want is to get a random question, each time the code is executed, Should I change the place where this random number is generated? Or am I doing wrong somewhere else?

Answer 1

You should be initializing random number generator using srand function using random seed value to change this behaviour of rand() function.
You can use something like srand (time(NULL)); to initialize random generator using different seed.
Please have look at http://www.cplusplus.com/reference/cstdlib/srand/

Answer 2

You are not seeding your random number generator so every time you run the program you will get the same sequence of random numbers. Use srand once at the start of the program.

Answer 3

You need to use function std::srand declared in header <cstdlib> that to set a random sequence.
For example
class English {
public:
English() { if ( !init ) std::srand( unsigned( std::time( 0 ) ) ); init = true; }
string get_questions (int number) const {
if (number == 1) {
// Chapter 1
string questions[10] = { /*...*/ };
string result = questions[rand() % 10] + "\n";
return result;
}
}
private:
static bool init;
};
bool English::init = false;
Take into account that i made changes in function get_questions

Answer 4

If you are using a C++11 compliant compiler, a better solution is to use the <random> library:
// initialize your string array
std::default_random_engine generator;
std::uniform_int_distribution<int> distribution(0,9);
int index = distribution(generator);
return questions[index];