Best Time to Buy and Sell Stock

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        #bruteforce - O(n^2)
        '''
        max_profit = 0
        n = len(prices)
        for i in range(n):
            j = i + 1
            while j < len(prices):
                if prices[j] > prices[i] and (prices[j] - prices[i]) > max_profit:
                    max_profit = prices[j] - prices[i]
                j += 1 
        return max_profit
        '''
        #improved - O(n) - Kadane's Algorithm
        buy = prices[0]
        max_profit = 0
        for i in range(1, len(prices)):
            if prices[i] < buy:
                buy = prices[i]
            elif prices[i] - buy > max_profit:
                max_profit = prices[i] - buy
        return max_profit