Data Structure/Algorithm Challenger II
Sometimes, while working with the list, it somehow gets corrupted. The corrupt node is pointing to some previous node instead of next node. So a circle is created in the list.
Test for the existence of circle (i.e., check if the list is corrupt).
Note: The list is doubly and not singly like Data Structure/Algorithm Challenger I, so a solution other then one specified in Data Structure/Algorithm Challenger I is expected.