You will get an array of numbers. 

Every preceding number is smaller than the one following it.

Some numbers will be missing, for instance:
```
[-3,-2,1,5] //missing numbers are: -1,0,2,3,4
```
Your task is to return an array of those missing numbers:
```
[-1,0,2,3,4]
```

Difficulty: EASY
Starter code: def find_missing_numbers(arr):
	

Solutions:
def find_missing_numbers(arr):
	if not arr:
		return []
	return sorted(set(range(arr[0] + 1, arr[-1])).difference(arr))


def find_missing_numbers(arr):
	return [x for x in range(arr[0], arr[-1] + 1) if x not in arr] if arr else []


import itertools

def find_missing_numbers(arr):
	return list(itertools.chain.from_iterable((range(a + 1, b) for (a, b) in zip(arr, arr[1:]))))


def find_missing_numbers(arr):
	if not arr:
		return arr
	(out, it) = ([], iter(arr))
	ref = next(it)
	for v in range(arr[0], arr[-1]):
		if v == ref:
			ref = next(it)
		else:
			out.append(v)
	return out


def find_missing_numbers(arr):
	if len(arr) < 2:
		return []
	return sorted(set(list(range(min(arr), max(arr)))) - set(arr))


def find_missing_numbers(arr):
	if len(arr):
		return [i for i in range(arr[0], arr[-1]) if i not in arr]
	else:
		return []


def find_missing_numbers(arr):
	try:
		return [i for i in range(arr[0], arr[len(arr) - 1]) if i not in arr]
	except IndexError:
		return []