Daily LeetCode 121. Best Time to Buy and Sell Stock

https://leetcode.com/problems/best-time-to-buy-and-sell-stock/

Easy

问题描述：

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Note that you cannot sell a stock before you buy one.

Example 1:

Input: [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
             Not 7-1 = 6, as selling price needs to be larger than buying price.

Example 2:

Input: [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.

思路及代码：

题目给定了一只股票的价格变化情况，我们只能够做一次买进卖出操作，要求最大利润。

我们只需要找出最低的买入价格以及最高的卖出价格，同时要注意，卖出只能在买进之后，我们只需要在一次遍历中更新最低价格和最大利润即可。

import sys

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        min_price, max_profit = sys.maxsize, 0

        for price in prices:
            min_price = min(price, min_price)
            current_profit = price - min_price
            max_profit = max(current_profit, max_profit)

        return max_profit