You are an expert Python programmer.
Write a Python code that defines a function named `solve` which takes one argument:
- a string representing CSV data with a header row.
The code must:
- parse the CSV string,
- return a list of dictionaries (one per row),
- keys are column names from the header, values are row entries,
- you may import the built-in 'csv' module if needed,
- raise a ValueError if the CSV is invalid.
Important formatting rules:
- Output only valid Python function code, nothing else.
- Enclose the code between <python_code> and </python_code> tags.
- Do not add explanations, comments, or test case.

