Need for predictable random generator

Question

I\'m a web-game developer and I got a problem with random numbers. Let\'s say that a player has 20% chance to get a critical hit with his sword. That means, 1 out of 5 hits

Answer 1

If you want a distribution that discourages repeat values, you could use a simple repeat rejection algorithm.

e.g.

int GetRand(int nSize)
{
    return 1 + (::rand() % nSize);
}
int GetDice()
{
    static int nPrevious=-1;
    while (1) {
        int nValue = GetRand(6);
        // only allow repeat 5% of the time
        if (nValue==nPrevious && GetRand(100)<95)
            continue;
        nPrevious = nValue;
        return nValue;
    }
}

This code rejects repeat values 95% of the time, making repeats unlikely but not impossible. Statistically it is a bit ugly, but it will probably produce the results you want. Of course, it won't prevent a distribution like "5 4 5 4 5". You could get fancier and reject the second last (say) 60% of the time and third last (say) 30%.

I'm not recommending this as good game design. Simply suggesting how to achieve what you want.