Class Shuffle problem

shuffleclass.py

from collections import deque

def shuffleClass(arr, n):
	if arr is None or len(arr) == 0: return []
	if n is None: return arr

	arr = deque(arr)
	if n >= 0:
		for _ in range(n % len(arr)):
			arr.appendleft(arr.pop())
	else:
		for _ in range(abs(n) % len(arr)):
			arr.append(arr.popleft())

	return list(arr)

print(shuffleClass([2,3], 3))

Hello @Fredpwol, thank you for participating in Week 6 of #AlgorithmFridays.

Not a bad attempt at a solution for Apex College; I like your use of the deque data structure - for more efficient removal/insertion operations. However, your solution failed the following test cases:

• When arr is an empty list and n has a negative value. Ideally your solution should return an empty list but it throws a IndexError: pop from an empty deque error on line 14.

• The other test your solution doesn't pass is for cases where n has a value greater than the size of the arr. For such cases, your solution returns the arr. For example, shuffleClass([2, 3], 3); // yours would return [2, 3] instead of [3, 2]. The expectation is that when the value of n is greater than the arr, you should think of it as shuffling the entire pupils list for as many times as is possible until n becomes less than the size of arr. In mathematical terms, that would be n= n % arr.length.

I understand that this solution was made with a lot of assumptions of how certain things should be implemented but I think it's always best to check in with your interviewer before making assumptions on how edge cases should be implemented. I wrote about that in this article, you might find it helpful.

Apart from that, this was a decent attempt. Please let me know your thoughts.

Hello @meekg33k, thanks for the feedback I really appreciate it, and I've updated my code to handle edge cases where I failed at. Thank you.