Best Time to Buy and Sell Stock (single transaction) (write full main, include follow-ups)

Problem: Best Time to Buy and Sell Stock (single transaction) (must provide runnable main, include follow-ups) Given an array prices where prices[i] is the stock price on day i, you may complete at most one transaction (buy once and sell once; must buy before sell). Return the maximum profit, or 0 if no profit is possible. Input (stdin) One line: integer array prices, e.g. [7,1,5,3,6,4] Output (stdout) One integer: the maximum profit Constraints 1 <= n <= 2 * 10^5 0 <= prices[i] <= 10^9 Follow-ups Unlimited transactions (cannot hold multiple shares at once). Add a 1-day cooldown after selling. Add a transaction fee fee per trade. Example Input [7,1,5,3,6,4] Output 5