CareerCup

c# solution:

public class Employee
        {
            public int Id { get; set; }
            public string Name { get; set; }
            public List<Employee> Reports { get; set; }
        }

 public static Employee ClosestCommonManager(Employee ceo, Employee firstEmployee, Employee secondEmployee)
        {
            Employee currentClosestManager = ceo;

            if (!Covers(ceo, firstEmployee) || !Covers(ceo, secondEmployee))
                return null;
            
            Queue q = new Queue();
            q.Enqueue(ceo);

            while (!q.IsEmpty())
            {
                var emp =(Employee) q.Dequeue();
                if (emp != null)
                {
                    foreach (var employee in emp.Reports)
                    {
                        if (Covers(employee, firstEmployee) && Covers(employee, secondEmployee) 
                            && (employee.Id != firstEmployee.Id && employee.Id != secondEmployee.Id))
                        {
                                currentClosestManager = employee;
                                q.Enqueue(employee);
                        }
                    }
                }
            }
            return currentClosestManager;

        }

        public static bool Covers(Employee root, Employee p)
        {
            if (root == null)
                return false;

            if (root.Id == p.Id)
                return true;

            foreach (var employee in root.Reports)
            {
                if (Covers(employee, p))
                {
                    return true;
                }
            }
            return false;
        }

//Driver program

public static void Test()
        {
            var bill = new Employee{Id = 1,Name = "Bill",Reports = new List<Employee>()};
            var dom = new Employee { Id = 2, Name = "Dom",Reports = new List<Employee>() };
            var samir = new Employee { Id = 3, Name = "Samir" ,Reports = new List<Employee>()};
            var michael = new Employee { Id = 4, Name = "Michael",Reports = new List<Employee>() };
            var bob = new Employee { Id = 5, Name = "Bob",Reports = new List<Employee>() };
            var peter = new Employee { Id = 6, Name = "Peter",Reports = new List<Employee>() };
            var porter = new Employee { Id = 7, Name = "Porter",Reports = new List<Employee>() };
            var milton = new Employee { Id = 8, Name = "Milton",Reports = new List<Employee>() };
            var nina = new Employee { Id = 9, Name = "Nina",Reports = new List<Employee>() };

            peter.Reports.Add(milton);
            peter.Reports.Add(nina);

            dom.Reports.Add(bob);
            dom.Reports.Add(peter);
            dom.Reports.Add(porter);

            bill.Reports.Add(dom);
            bill.Reports.Add(samir);
            bill.Reports.Add(michael);

            var ccm = ClosestCommonManager(bill, milton, nina);
            Console.WriteLine(ccm.Name);

            ccm = ClosestCommonManager(bill, nina, porter);
            Console.WriteLine(ccm.Name);

            ccm = ClosestCommonManager(bill, nina, samir);
            Console.WriteLine(ccm.Name);

            ccm = ClosestCommonManager(bill, peter, nina);
            Console.WriteLine(ccm.Name);
        }