Best Time to Buy and Sell Stock with Cooldown.py

class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        size = len(prices)
        if not size:
            return 0
        buys = [None] * size
        sells = [None] * size
        sells[0], buys[0] = 0, -prices[0]
        for x in range(1, size):
            delta = prices[x] - prices[x-1]
            sells[x] = max(buys[x-1]+prices[x], sells[x-1]+delta)
            buys[x] = max(buys[x-1]-delta, sells[x-2]-prices[x] if x>1 else None)
            
        return max(sells)