Objective C Merge Sort

mergeSort

- (NSArray*) mergeSortArray:(NSArray*) arr {
  	if(arr.count <2) {
		return arr;
    }
    
    NSUInteger middle = arr.count/2;
    NSRange leftRange = {0,middle};
    NSArray *leftArray = [arr subarrayWithRange:leftRange];
    NSRange rightRange = {middle,arr.count-middle};
    NSArray *rightArray = [arr subarrayWithRange:rightRange];
    
    leftArray = [self mergeSortArray:leftArray];
    rightArray = [self mergeSortArray:rightArray];
    
    return [self mergeLeftArray:leftArray andRightArray:rightArray];
    
}

- (NSArray*)mergeLeftArray:(NSArray*)leftArray andRightArray:(NSArray*)rightArray {
	NSMutableArray *sortedArray = [[NSMutableArray alloc] init];
	NSMutableArray *mutableLeft = [leftArray mutableCopy];
    NSMutableArray *mutableRight = [rightArray mutableCopy];
    
	while (mutableLeft.count >0 || mutableRight.count >0) {
		if(mutableLeft.count >0 && mutableRight.count >0) {
			if([mutableLeft[0] floatValue] <= [mutableRight[0] floatValue]) {
                [sortedArray addObject:mutableLeft[0] ];
				[mutableLeft removeObjectAtIndex:0];
				
			} else {
                [sortedArray addObject:mutableRight[0]];
				[mutableRight removeObjectAtIndex:0];
				
            }
		} else if(mutableLeft.count >0) {
            [sortedArray addObject:mutableLeft[0]];
			[mutableLeft removeObjectAtIndex:0];
			
        } else {
            [sortedArray addObject:mutableRight[0]];
            [mutableRight removeObjectAtIndex:0];
			
        }
	}
	return sortedArray;
    
}