Let’s say we have sequence A and subsequence of A, called B. I need to determine which elements of sequence A could be potentially used to construct subsequence B.

What will be the time complexity of the Code below, as my teacher said the time complexity will be O(N2^N).
My question, as per my understanding of how T.C(which might be very wrong, so please don’t judge) is calculated by seeing how many times the loop will be running as the input grows.
So as per my thinking, T.C should be O(N2^(N-1)), as when we will process 3 it will run 4 times and when it will process 4 it will run 8 times.
Please help me understanding it. Moreover, my teacher is not responding to my questions, so that’s why I cam over here.