[herge]

If the linked list has a loop, but you don't know it, how do you figure out the length of the list to allocate enough space for your array? How do you copy the list into the array without traversing the list? How do you traverse the list without hitting the loop and looping infinitely?

[dllthomas]

If you know that all the elements in the loop are already in the array then traversing it is easy. Of course, if you have an upper bound for the length of the list, there's an easier check...