I'm trying to write a way to generate a random array of X numbers,
and
the numbers need to be between 0 and X, and not be repeating (its for
generating a random playlist.)
Just generate the random playlist directly, don't bother with indexes.
Put the tracks into an array, then use the canonical shuffle algorithm
which, in pseudocode, is:
for i from 0 to array_length - 2
random_index = random in [i, array_length - 1]
swap array[i] with array[random_index]
Transforming this into real code is left as an exercise for the
reader.
@implementation NSMutableArray (Shuffling)
- (void)shuffle
{
int max = [self count] -1;
int i;
for (i = 0; i < max; i++) {
int choice = random() % max;
[self swapObjectAtIndex:i withObjectAtIndex:choice];
}
}
- (void)swapObjectAtIndex:(unsiged)a withObjectAtIndex:(unsiged)b
{
id temp = [self objectAtIndex:a];
[self replaceObjectAtIndex:a withObject:[self objectAtIndex:b]];
[self replaceObjectAtIndex:b withObject:temp];
}
@end
Best Regards,
Nir Soffer
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