void generator() 
{
    int n = <some number>;
    srand(n);
    int first = randint(9);
    digits.push_back(first);
    while (digits.size() < 4) 
    {
        bool flag = true;
        int num = randint(9);
        for (int j = 0; j < digits.size(); j  ) 
        {
            if (num == digits[j]) 
            {
                flag = false;
                break;
            }
        }
        if (flag == true) 
        {
            digits.push_back(num);
        }
    }
    for (int i : digits)
    {
        cout << i << " ";
    }
}

int main() 
{
 generator();
}

This code is supposed to generate 4 random and distinct digits on execution.

randint(x) is a function which generates a single random value anywhere between 0 and x.

While my digits are distinct, they aren't random. No matter what value I put inside srand(), I'm getting the same four digits:

2 4 5 1

Help me out if I'm doing something wrong.

CodePudding user response：

std::experimental::randint is coupled with std::experimental::reseed to set the seed per thread: srand will have no effect on the generated output. You'll probably find that randint is automatically seeded with a constant value which accounts for your output. As it never became part of the C standard, I cannot comment further with certainty.

This is all non-standard, all non-portable, and best avoided from C 11 now we have <random>.