What's the Best Way to Shuffle an NSMutableArray?

Question

If you have an NSMutableArray, how do you shuffle the elements randomly?

(I have my own answer for this, which is posted below, but I\'m new to Cocoa an

Answer 1

If elements have repeats.

e.g. array: A A A B B or B B A A A

only solution is: A B A B A

sequenceSelected is an NSMutableArray which stores elements of class obj, which are pointers to some sequence.

- (void)shuffleSequenceSelected {
    [sequenceSelected shuffle];
    [self shuffleSequenceSelectedLoop];
}

- (void)shuffleSequenceSelectedLoop {
    NSUInteger count = sequenceSelected.count;
    for (NSUInteger i = 1; i < count-1; i++) {
        // Select a random element between i and end of array to swap with.
        NSInteger nElements = count - i;
        NSInteger n;
        if (i < count-2) { // i is between second  and second last element
            obj *A = [sequenceSelected objectAtIndex:i-1];
            obj *B = [sequenceSelected objectAtIndex:i];
            if (A == B) { // shuffle if current & previous same
                do {
                    n = arc4random_uniform(nElements) + i;
                    B = [sequenceSelected objectAtIndex:n];
                } while (A == B);
                [sequenceSelected exchangeObjectAtIndex:i withObjectAtIndex:n];
            }
        } else if (i == count-2) { // second last value to be shuffled with last value
            obj *A = [sequenceSelected objectAtIndex:i-1];// previous value
            obj *B = [sequenceSelected objectAtIndex:i]; // second last value
            obj *C = [sequenceSelected lastObject]; // last value
            if (A == B && B == C) {
                //reshufle
                sequenceSelected = [[[sequenceSelected reverseObjectEnumerator] allObjects] mutableCopy];
                [self shuffleSequenceSelectedLoop];
                return;
            }
            if (A == B) {
                if (B != C) {
                    [sequenceSelected exchangeObjectAtIndex:i withObjectAtIndex:count-1];
                } else {
                    // reshuffle
                    sequenceSelected = [[[sequenceSelected reverseObjectEnumerator] allObjects] mutableCopy];
                    [self shuffleSequenceSelectedLoop];
                    return;
                }
            }
        }
    }
}