123. Best Time to Buy and Sell Stock III

class Solution {
    public int maxProfit(int[] prices) {
        int n = prices.length;
        if (n == 0) return 0;
        
        int buy1 = -prices[0];
        int sell1 = 0;
        int buy2 = -prices[0];
        int sell2 = 0;
        for (int i = 1; i < n; i++) {
            buy1 = Math.max(buy1, -prices[i]);
            sell1 = Math.max(sell1, buy1 + prices[i]);
            buy2 = Math.max(buy2, sell1 - prices[i]);
            sell2 = Math.max(sell2, buy2 + prices[i]);
        }
        
        return Math.max(sell1, sell2);
    }
}