Employee Hierarchy Add / Delete

Design an employee hierarchy class that supports adding employees under managers and deleting employees by id. Follow-ups cover deleting managers, deleting the CEO, cycle handling, and choosing a replacement manager by seniority. Requirements Build an employee class / hierarchy manager. addEmployee(employee_id, manager_id): add an employee under an existing manager; the manager is guaranteed to be added before the employee. deleteEmployee(employee_id): remove an employee by id. Handle manager deletion, CEO deletion, and invalid structures such as reporting cycles. Follow-up: each employee has a level / seniority. When deleting a manager, promote the most senior employee in that manager's group as the replacement; if multiple employees share the highest level, choose the one who joined earliest. Notes Use maps from id to node and id to children; keep parent pointers so deletes do not require a full traversal. CEO deletion needs an explicit policy: reject, promote a child, or create a new root. State the policy and keep it consistent. For the seniority follow-up, maintain insertion order on nodes and compare (level desc, insertion_order asc). Preparation Implement tree mutation operations with parent pointers. Practice deleting an internal node while reconnecting children. Add cycle checks with DFS or parent-chain walking before accepting a new edge.