Reformat Department Table

Many organizations store department information in a flat, unstructured format. This challenge asks you to reformat this data into a more structured table, grouping employees by department and sorting them alphabetically within each department. This is useful for generating reports, improving data analysis, and generally making the data more accessible.

Problem Description

You are given a list of employee records. Each record is a string containing the employee's name and department, separated by a comma. Your task is to reformat this data into a table where each department is a row, and the employees within that department are listed as a comma-separated string. The employees within each department should be sorted alphabetically.

What needs to be achieved:

• Parse the input list of employee records.
• Group employees by their department.
• Sort the employees alphabetically within each department.
• Format the output as a comma-separated string of departments, where each department contains a comma-separated list of employees.

Key Requirements:

• Handle cases where a department has no employees.
• Handle cases where the input list is empty.
• Ensure the output is correctly formatted as specified.
• Employee names and department names are case-sensitive.

Expected Behavior:

The function should return a string representing the reformatted table. The string should contain each department name followed by a comma and then a comma-separated list of employees in that department, sorted alphabetically.

Edge Cases to Consider:

• Empty input list.
• Departments with no employees.
• Duplicate employee names within a department.
• Input strings with extra commas or spaces. (Assume these are invalid and should be ignored - focus on the core name/department pairing)

Examples

Example 1:

Input: ["Alice,Engineering", "Bob,Sales", "Charlie,Engineering", "David,Sales"]
Output: "Engineering,Alice,Charlie,Sales,Bob,David"
Explanation: Employees are grouped by department ("Engineering" and "Sales"). Within each department, employees are sorted alphabetically ("Alice,Charlie" and "Bob,David"). The departments are then concatenated with commas.

Example 2:

Input: ["Alice,Engineering", "Bob,Sales", "Charlie,Engineering", "David,Sales", "Eve,Marketing"]
Output: "Engineering,Alice,Charlie,Marketing,Eve,Sales,Bob,David"
Explanation:  All departments are included, and employees are sorted alphabetically within each.

Example 3:

Input: []
Output: ""
Explanation: An empty input list results in an empty output string.

Example 4:

Input: ["Alice,Engineering", "Bob,Engineering"]
Output: "Engineering,Alice,Bob"
Explanation: Demonstrates sorting within a single department.

Constraints

• The input list will contain strings of length between 5 and 50 characters.
• Employee names and department names will contain only alphanumeric characters and spaces.
• The number of employee records in the input list will be between 0 and 1000.
• The performance should be reasonable for the given constraints (avoiding excessively complex algorithms).

Notes

Consider using a dictionary (or hash map) to group employees by department. Sorting the employee lists within each department is a crucial step. Think about how to efficiently concatenate the departments and employees into the final output string. The order of departments in the output is not specified, so any valid ordering is acceptable.