# How to differentiate an infinite linked list versus a linked list with cycle?

• Suppose you have two linked lists.  One is infinite meaning when you start at the beginning and go to the next node you will always get a next node.  One is circular meaning the last element points to the first element.  For this list the same condition holds - you will always get a next node. Given one of these lists, how do you determine if it's the circular one or not?

I consider this problem is slightly different from the original one. Is there a solution to my problem?

• if the list is infinite, you can never tell the list has a circle or not.

The thing is , if all you can do is to check the next node, when the list is infinite, you have no method to judge the list is finite or infinite.

• I think you can. You just need to go through the list and mark every element with some flag (in this case - you can set value to null/None), and if you find the makred item - it has lists, if you come to the end of the linked list - it doesn't.

For some reason such code will also work for this task at least for Python :)

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