Strengths:

• The solution is efficient with O(n) time complexity, which is optimal for this problem.
• The code is concise and easy to understand.
• The use of HashMap for O(1) lookups is appropriate and well-implemented.

Areas for Improvement:

• The variable name valueDiffMap might be slightly misleading. Since the map stores the array value as the key and its index as the value, a more descriptive name like valueToIndexMap would be clearer.
• It's good practice to specify the initial capacity of the HashMap to avoid resizing overhead. Given the constraints (n up to 10^4), you can initialize it as new HashMap<>(nums.length) to improve performance.
• Although the problem states there is exactly one solution, it's still good practice to handle the case where no solution is found (which the code does by returning [-1, -1]).
• Consider adding a comment to explain the approach briefly, which can be helpful for readability.

Overall, the solution is correct and efficient. The minor naming issue does not affect functionality.