121-123. Best Time to Buy and Sell Stock I & II & III [Easy & Hard] 买卖股票

最新推荐文章于 2019-10-30 17:17:29 发布

木木歹朱

最新推荐文章于 2019-10-30 17:17:29 发布

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本文链接：https://blog.youkuaiyun.com/qq_35319215/article/details/96921162

本文深入探讨了三种不同条件下的股票买卖策略算法，包括仅能买卖一次、可进行多次买卖及允许两次买卖的情况。每种策略都详细介绍了其时间复杂度为O(n)的高效算法实现，通过Python代码示例，读者可以清晰理解如何在不同限制下最大化利润。

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121. Best Time to Buy and Sell Stock

只能买卖一次
时间复杂度：O(n)

代码如下：

class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        res = 0
        buy = float('-inf')
        for i in prices:
            buy = max(buy, -i)
            res = max(res, buy+i)
        return res

122. Best Time to Buy and Sell Stock II

多次买卖
时间复杂度：O(n)

代码如下：

class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        res = 0
        for i in range(1, len(prices)):
            if prices[i] > prices[i-1]:
                res += prices[i] - prices[i-1]
        return res

123. Best Time to Buy and Sell Stock III

买卖两次
时间复杂度：O(n)

代码如下：

class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        buy1 = buy2 = float('-inf')
        sale1 = sale2 = 0
        for i in prices:
            buy1 = max(buy1, -i)
            sale1 = max(sale1, buy1 + i)
            buy2 = max(buy2, sale1 - i)
            sale2 = max(sale2, buy2 + i)
        return sale2