Completed DP 2 problems

[thondaha]

No description provided.

[super30admin]

The student's solution is excellent overall. Here are some minor suggestions for improvement:

• The helper method names (e.g., helperRec, helperMemo) could be more descriptive to indicate their purpose more clearly.
• The comments are helpful, but adding a brief explanation of the DP state transition for each approach could further enhance understanding.
• The test cases are good, but adding edge cases (e.g., large input sizes) could further validate the robustness of the solution.