Shuffle Randomize an NSMutableArray excepting item at index0 - ios

Question

Have an NSMutableArray, and when my users press a button, I'd like all items in the array to randomly change position, !! except for the first !!.
Right now I have
-(void)shufflemyList{
NSLog(#"Un Shuffled array : %#",myList);
NSMutableArray *array = [NSMutableArray arrayWithCapacity:0];
while ([myList count] > 0)
{
int index = arc4random() % [myList count];
id objectToMove = [myList objectAtIndex:index];
[array addObject:objectToMove];
[myList removeObjectAtIndex:index]; }
// test
NSLog(#"Shuffled array : %#",array);
myList=array; }
This works to completely shuffle the list.
Is there a way to shuffle the whole list, excepting the first item?

Answer 1

Just add 2 lines
-(void)shufflemyList{
NSLog(#"Un Shuffled array : %#",myList);
NSMutableArray *array = [NSMutableArray arrayWithCapacity:0];
// new code ---
[array addObject:myList[0]];
[myList removeObjectAtIndex:0];
// ---
while ([myList count] > 0)
{
int index = arc4random() % [myList count];
id objectToMove = [myList objectAtIndex:index];
[array addObject:objectToMove];
[myList removeObjectAtIndex:index]; }
// test
NSLog(#"Shuffled array : %#",array);
myList=array; }
Also it is better to use 'arc4random_uniform(n)' instead of 'arc4random() % n'. From docs:
arc4random_uniform() will return a uniformly distributed random number
less than upper_bound. arc4random_uniform() is recommended over
constructions like ``arc4random() % upper_bound'' as it avoids "modulo
bias" when the upper bound is not a power of two.