{wwR, where w is a string of a and b} is non deteministic CFL because till half of the length, we have to push and then we have to pop. but we dont know length. So at each step, we will push the next symbol and pop the previous one to see which one works. so it is non deteminsitic. So a CFL will be either deterministic or non deterministic but in case by w#wR we know that at # we have to stop pushing and after # we start popping hence it is DPDA.