EASY leetcode 121 best time to sell and buy stock - slid window

https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
121. You are given an array prices where prices[i] is the price of a given stock on the ith day.

You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.

Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.

Example 1:

Input: prices = [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.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.
Example 2:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transactions are done and the max profit = 0.

Constraints:

1 <= prices.length <= 105
0 <= prices[i] <= 104

class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        
        buy, sell = 0, 1  # the days of buying and selling stocka
        
        profit = 0
        
        while sell < len(prices):
            if prices[sell] < prices[buy]: # find a lower price and we can buy stock this day
                buy = sell
            else:
                profit = max(profit, prices[sell]-prices[buy])
            sell += 1
        return profit
        # time comlexity o(n), memory complexity o(1)