Apigee Principal Software Engineer interview questions

In person interview process was easy but i am not happy about the part the person who was asking coding question was not not sure what he is asking. He asked me permutation and combination coding question and I felt he himself did not know difference between permutation and combination. I wrote code of combination using power set approach and he did not know what is power set so he could not understand the code which i wrote. So now if interviewer does not know the question himself then how he can judge any candidate. He was too casual in interview randomly asking anything but if i asked questions then he himself will get confused what he is asking i felt he was not prepared for taking interviews. After this process i get email next day they do not want to move forward. Overall very bad interview experience.