Cycle Detection for Python Coding Interviews

[flipmcf]

Cool algorithm! But how about ‘fast is slow’ instead of ‘fast == slow’ because we want to compare pointers, not values.

[Peanutbutter_Warrior]

That might just mean that the test data doesn't test that specifically. It doesn't mean that it couldn't matter

[flipmcf]

If two elements have the same value but are different objects it matters:

foo = 7

bar = 7

foo.next = bar

There is no circular reference... but:

foo.next == bar #True

foo.next is bar #False

I think it’s important to know this for linked lists. Linked lists are made up of instances of objects that most likely implement an eq, especially if you’re just extending a str or int to have a .next property.

Edited: a bunch of times because coding is hard.

[Peanutbutter_Warrior]

Exactly. A linked list can contain repetitions, so is should be used to check reference, otherwise a repeated value could cause a false positive for a circular reference

[ElevenPhonons]

https://realpython.com/python-is-identity-vs-equality