Strengths:

• The student has demonstrated a strong understanding of the problems and has provided efficient solutions.
• The use of in-place modifications and clever tricks to achieve optimal performance is commendable.
• The code is well-commented and easy to follow.

Areas for Improvement:

• In Problem 3, the space complexity is mentioned as O(), which is incomplete. It should be specified as O(1) since the solution uses in-place modifications.
• The student could consider adding more detailed comments or docstrings for the helper functions to explain their purpose and parameters.
• For Problem 2, the student could add a brief explanation of the approach in the comments to enhance readability.