Java DS Problem Solving Assistance Needed

I'm looking for a skilled Java programmer with strong data structures (DS) knowledge and problem-solving skills. I have two specific problems that involve Arrays and Lists.

The primary goal is to find solutions that can help me learn and understand the concepts better. Therefore, clear explanations and well-structured code will be highly appreciated.

The problems should be solved using both iterative and recursive approaches.

Ideal skills for this project include:
- Proficiency in Java programming language
- Strong understanding of data structures
- Excellent problem-solving abilities
- Experience in teaching or explaining complex concepts
- Familiarity with both iterative and recursive approaches

Need Help solving two Java DS Problem scenarios