Cooldown plus a transaction fee
Asked at Optiver
Given daily prices and a fixed fee on every completed round trip, you may trade unlimited round trips (at most one share), with a one-day cooldown after each sell.
prices = [1, 4, 0, 0, 5], fee = 1
-> 6 # buy@1 sell@4 (net 2), cooldown, buy@0 sell@5 (net 4)
Return the maximum profit. Aim for time, space.
Your answer
This one is open-ended. Work it through, then check your reasoning against the full solution.