This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Assuming that you already have the list of lists structure, what you need to do is to figure out:
1. How to traverse this structure
2. How to combine the lists that should be merged (See the hint from the previous post)
3. How to collect the merged lists into the final list (If you managed to build up the list of lists structure this is done )