[220201] Best Time to Buy and Sell Stock

class Solution:
    def maxProfit(self, prices):

        # 记录最高利润、最低成本
        res = 0
        min_price = prices[0]

        for i in range(1, len(prices)):
            min_price = min(min_price, prices[i])
            res = max(res, prices[i] - min_price)

        return res

class Solution:
    def maxProfit(self, prices):

        # left: buy; right: sell
        left, right = 0, 1
        res = 0

        while right < len(prices):
            profit = prices[right] - prices[left]
            if profit > 0:
                res = max(res, profit)
            else:
                left = right
            right += 1

        return res