Question

Given circuits for f and f−1, we can create classical reversible circuits Rf, R−1f, Rf−1, R−1f−1 which are shown in the following figure. (Assume that f is a bijection.)In what sequence shall we apply the above circuits in order to implement a reversible circuit that on input x outputs f(x) reversibly? Write your answer in terms of A, B, C, and D using comma as a delimiter. (For example: B,C,A)