How you code arc4random() that does not repeat number twice?
For instance. I'm using switch and button. I don't want to generate reused the same arc4random number again. If I have arc4random that generation numbers 2,4,42,32,42... I don't want to 42 to appear again.
How do I avoid this?
switch (arc4random() % 50 )
{
case 1:
text.text = @"You are silly boy";
break;
case 2:
text.text = @"Well, you very very silly"];
break;
case 3:
text.text = @"stop being silly"];
break;
case 4:
[text.text = @"silly... silly"];
break;
case 5:
text.text = @"what you silly boy"];
break;
...
case 0:
text.text = @"you silly"];
break;
}
One way of doing it would be as follows:
static int maxNumOfCases = 50; //This could be any number of cases that you need in your app.
......
switch (arc4random() % (maxNumOfCases--)) {
case 1:
text.text = @"You are silly boy";
break;
case 2:
text.text = @"Well, you very very silly"];
break;
case 3:
text.text = @"stop being silly"];
break;
case 4:
[text.text = @"silly... silly"];
break;
case 5:
text.text = @"what you silly boy"];
break;
...
case 0:
text.text = @"you silly"];
break;
}
This code always switches to a unique case on each invocation. The way the code works is by decreasing the range of arc4random() at each invocation by 1.
Update: Keep note that this method biases more towards the end of the run to a smaller range of numbers. So this is not a true non-repeating random number generation. But if thats not a concern, its an easy one liner to include in your code.