Sorting an array by Parent-Child - ios

Question

I have an array of custom objects. The objects represent segments in a binary file.
The property loc holds the objects own location in the file, where prev holds the location of the "previous" object. In this context "previous" and "next" doesn't necessarily mean that the objects occur after each other in the file.
The first object has prev = 0. The last object has no following object holding its location as prev.
How do I achieve such kind of sorting? Number of objects is initially not known.
//My custom object
#interface MyObject : NSObject
#property (nonatomic, assign) NSInteger loc, prev;
#end
//In the implementation of some other class
NSMutableArray *array = [NSMutableArray new];
{// order should be 6
MyObject *obj = [MyObject new];
obj.loc = 3000;
obj.prev = 111;
[array addObject:obj];
}
{// order should be 2
MyObject *obj = [MyObject new];
obj.loc = 2000;
obj.prev = 222;
[array addObject:obj];
}
{// order should be 4
MyObject *obj = [MyObject new];
obj.loc = 333;
obj.prev = 4000;
[array addObject:obj];
}
{// order should be 1
MyObject *obj = [MyObject new];
obj.loc = 222;
obj.prev = 5000;
[array addObject:obj];
}
{// order should be 5
MyObject *obj = [MyObject new];
obj.loc = 111;
obj.prev = 333;
[array addObject:obj];
}
{// order should be 3
MyObject *obj = [MyObject new];
obj.loc = 4000;
obj.prev = 2000;
[array addObject:obj];
}
{// order should be 0
MyObject *obj = [MyObject new];
obj.loc = 5000;
obj.prev = 0;
[array addObject:obj];
}

Answer 1

Try using lexicographical sorting:
NSArray *sorted = [array sortedArayUsingComparator:^(id obj1, id obj2) {
if ([obj1 parentID] < [obj2 parentID] {
return NSOrderedAscending;
} else if ([obj1 parentID] > [obj2 parentID] {
return NSOrderedDescending;
} else if ([obj1 ID] < [obj2 ID] {
return NSOrderedAscending;
} else if ([obj1 ID] > [obj2 ID] {
return NSOrderedDescending;
} else {
return NSOrderedSame;
}
}];

Answer 2

Never mind, I got it.
NSMutableArray *unordered = [[NSMutableArray alloc] initWithArray:array];
NSMutableArray *ordered = [NSMutableArray new];
for(MyObject *myObj in array)
{
if(!myObj.prev)
{
[orderedTables addObject:myObj];
[unorderedTables removeObject:myObj];
break;
}
}
int counter = 0;
while(unordered.count && counter < ordered.count)
{
MyObject *obj1 = [ordered objectAtIndex:counter++];
for(int i = 0; i < unordered.count; ++i)
{
MyObj *obj2 = [unordered objectAtIndex:i];
if(obj2.prev == obj1.loc)
{
[ordered addObject:obj2];
[unordered removeObject:obj2];
break;
}
}
}