Given a 5-day price chart, buy and sell a single stock to maximize profit — with one twist. After you sell, you must wait one full day before buying again (the “cooldown”). Realized profit = cash in hand at the end; no holding past day 4.
Why is +3 the answer — not +4? The cooldown rewrites your plan. You'll feel it. Start here: you know the clean two-situation model (holding, not holding). One circle: HOLDING. You own a stock. But wait — how do you get INTO HOLDING on day 0 if you don't own one yet?
You tried to buy on day 1 but your single circle has nowhere to send you. Before we add more circles, predict — what goes wrong with a one-circle model?
Answer the prediction to continue.