0- means before the commutation and 0+ after commutation. In capacitor the voltage before and after are equal U(0-)=U(0+).Or there would be a infinite change in voltage du/dt.
I=Cdu/dt. You have to find the voltage on the capacitor.Since the energy before and after the commutation is equal W(0-)=W(0+). You have a relation about energy W=C*U^2/2. You find the intial value for voltage.The final value of the capacitor`s voltage is zero,because it has been discharged.So...