Question

I have 2 numbers which are between 0 and 49. Let’s call them x and y. Now I want to get a couple of other numbers which are not x or y, but are also between 0 and 49 (I am using Objective C but this is more of a general theory question I think?).

Method I thought of is:

 int a;
 int b;
 int c;

 do {
  a = arc4random() % 49;
 } while ((a == x) || (a == y));

 do {
  b = arc4random() % 49;
 } while ((b == x) || (b == y) || (b == a));

 do {
  c = arc4random() % 49;
 } while ((c == x) || (c == y) || (c == a) || (c == b));

But it seem kind of bad to me, I don’t know, I am just trying to learn to be a better programmer, what would be the most elegant way to do this for best practices?

Answer 1

You can use something called the Fisher-Yates shuffle. It’s an efficient algorithm for producing a randomly ordered list of values from some set. You would first exclude N from the list of values from which to get random values, and then perform the shuffle.