std::rand() create same string

Ketan__Patel__0011

Hello Friends and Qt Experts.

Right now i am working on Randomization
i want to Generate unique string from my software every time.

Here is my code.

QString MainWindow::GenerateRandomString(int StringLength)
{
    const QString PossibleCharacters("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789");
    QString RandomGeneratedString;
    for(int i = 0; i < StringLength; i++)
    {
        int index = std::rand() % PossibleCharacters.length();
        QChar NextCharacter = PossibleCharacters.at(index);
        RandomGeneratedString.append(NextCharacter);
    }
    return RandomGeneratedString;
}

this function working well n good

but when i restart the my application
i am getting same string which is previously generated.(Before restart the Application.)

Result is ::

/////// First Time Generated Strings ///////
F98ER24S8U
R3ZPZXH0DA
1YOJE8760X
LSLS7E9TH4
LPCV7UVH32

/////// Second Time Generated Strings (After Restart The Application) ///////
F98ER24S8U
R3ZPZXH0DA
1YOJE8760X
LSLS7E9TH4
LPCV7UVH32

Please help me to solve my problem.
Thanks in advance.

Chris Kawa

With std::rand() you need to seed your generator with a different value. Traditionally a common choice is current time. A more modern one is std::random_device. See std::srand() for details.

As a side note - rand() and % is not a very good way to generate random numbers in a range. It can result in a biased distribution. If you want a number from a given range use a proper dedicated distribution function: std::uniform_int_distribution.

jsulm

@Ketan__Patel__0011 Sounds like you forgot to initialise the random generator

std::srand(std::time(nullptr)); // use current time as seed for random generator

See https://en.cppreference.com/w/cpp/numeric/random/rand