leetcode 714 买卖股票的最佳时机含手续费

这题好难思考。。。根据以前买股票经验，只需要将手续费减掉就好。这里有个思想，就是转换，如手续费为2, [3, 8, 9]，算 3 到 9很麻烦，可先算 3 到 8，在算 8 到 9，最后等同于 3 到 9，这就需要条件转换了。

class Solution(object):
    def maxProfit(self, prices, fee):
        """
        :type prices: List[int]
        :type fee: int
        :rtype: int
        """
        answer = 0
        buyPrice = float('inf')
        for price in prices:
            if price < buyPrice:
                buyPrice = price
                continue
            if price > buyPrice + fee:
                answer += price - buyPrice - fee
                buyPrice = price - fee
        return answer