random numbers

**mesmer** · 10-24-2008

I know that you can scale random numbers down to a range that you want. For instance I know that I can generate a random number between [m,n] inclusive.
What I want to do is generate a random number between [m,n], BUT I want to exclude certain numbers in this range. For example let's say that I wanted to generate a random number between 4 and 10,but I want to exclude 6 and 8. How could I do that? Is it just as simple as something like this:

rand() !=6 && !=8;

I know that the above code is not correct,but am I on the right track?

As an addendum as I continue to generate random numbers I want to exclude the random numbers that I have generated. For example lets say that I generate 7, now I want to exclude 6,8,and 7

**QuantumPete** · 10-24-2008

No, you can't do it like that. You will need to store every random number you generated in an array or linked list and then discard a generated random number if it is in that list.

QuantumPete

**C_ntua** · 10-24-2008

Code:

int excluded[] = {6,8};
int genRand() {
    int myNumber = (rand() % (n+1)) + m;
    for (int i = 0; i < sizeof(excluded) / sizeof(excluded[0]); ++i)
        if (myNumber == excluded[i]) {
            myNumber = genRand();
            break;
        }
    return myNumber;
}

or something like that

**tabstop** · 10-24-2008

Perhaps you want a random shuffle of the allowed numbers.

**mesmer** · 10-24-2008

Originally Posted by C_ntua

Code:

int excluded[] = {6,8};
int genRand() {
    int myNumber = (rand() % (n+1)) + m;
    for (int i = 0; i < sizeof(excluded) / sizeof(excluded[0]); ++i)
        if (myNumber == excluded[i]) {
            myNumber = genRand();
            break;
        }
    return myNumber;
}

or something like that

Thanks for the help, have not had time to try this out yet. Can't wait to get to my editor.

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