Best Time to Buy and Sell Stock with Cooldown

def maxProfit(prices):
    dp = {} # key=(i, buying) val=max_profit
    def dfs(i, buying):
        if i >= len(prices):
            return 0
        if (i, buying) in dp:
            return dp[(i, buying)]
            
        if buying:
            buy = dfs(i + 1, not buying) - prices[i]
            cooldown = dfs(i + 1, buying)
            dp[(i, buying)] = max(buy, cooldown)
        else:
            sell = dfs(i + 2, not buying) + prices[i]
            cooldown = dfs(i + 1, buying)
            dp[(i, buying)] = max(sell, cooldown)
            
        return dp[(i, buying)]
        
    return dfs(0, True)