[leetcode] problem 714 – best time to buy and sell stock with transaction fee

// sell[i]: Max profit till index i. The series of transaction is ending with a sell.
// buy[i] = max(buy[i - 1], sell[i - 1] - prices[i])
// sell[i] = max(sell[i - 1], buy[i - 1] + prices[i] - fee)
public int (int[] prices, int fee) {
    if (prices == null || prices.length <= 1)
            return 0;

    int b0, b1 = -prices[0];
    int s0 = 0, s1 = 0;

    for (int i = 1; i < prices.length; i++) {
        b0 = Math.max(b1, s1 - prices[i]);
        s0 = Math.max(s1, b1 + prices[i] - fee);

        b1 = b0;
        s1 = s0;
    }

    return s0;
}