Datawhale编程实践（LeetCode 腾讯精选练习50）Task10

1.买卖股票的最佳时机https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock/

拿到这题首先想到最暴力的方法，遍历

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        max_profit = 0
        for i in range(len(prices) - 1):
            for j in range(1, len(prices) - i):
                max_profit = prices[i+j] - prices[i] if prices[i+j] - prices[i] > max_profit else max_profit
        return max_profit

但是超出时间限制了

看到了官方的“历史最低点”方法，仔细思考了一下确实很有道理，只需要遍历一次，思想类似于动态规划。

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        inf = int(1e9)
        minprice = inf
        maxprofit = 0
        for price in prices:
            maxprofit = max(price - minprice, maxprofit)
            minprice = min(price, minprice)
        return maxprofit

 

2.买卖股票的最佳时机 IIhttps://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-ii/

这一题感觉比上一题更简单，只要后一天比第一天涨了就可以将差值加到结果里面。相当于贪心算法

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        max_profit = 0
        for i in range(len(prices) - 1):
            max_profit += prices[i+1] - prices[i] if prices[i+1] - prices[i] > 0 else 0
        return max_profit

执行用时超越99.41%

 

3.