changing probability of getting a random number

Question

I would like to generate a random number between 0 and 3 and I have the following in my code:

int random = rand() % 4;

This works fine but

Answer 1

Just code exactly what you want:

int myrand(void)
{
    const int percentZero = 10;
    if ((rand()%100) < percentZero) return 0;
    return 1 + (rand() % 3);
}

You can change the percentage of time zero is returned to whatever you want.