https://leetcode.com/problems/populating-next-right-pointers-in-each-node/\nhttps://leetcode.com/problems/flatten-a-multilevel-doubly-linked-list/\n\nProblems like those listed above with more custom linked list classes (with additional pointers) have serialization bugs. The output never matches the expected output even when you use the solutions from any of the discuss posts.

https://leetcode.com/problems/populating-next-right-pointers-in-each-node/\nhttps://leetcode.com/problems/flatten-a-multilevel-doubly-linked-list/\n\nProblems l