Merge two sorted linkedList
The name of the method is mergeLists, not mergeNodes. Even though you may think your method is simpler, using Nodes as parameters is misleading for the current method name. One way to address this issue is to rename the method as mergeListsUsingTheirHeads or, to be specific to the problem of merging sorted lists, mergeSortedListsUsingTheirHeads.

I have to ask: what made you think your code is simpler than that of the post you mentioned?