121.md

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        profit = 0
        
        for i, buy_price in enumerate(prices[:-1]):
            for sell_price in prices[i:]:
                trade_profit = sell_price - buy_price
                if trade_profit > profit:
                    profit = trade_profit
                    
        return profit

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        profit = 0
        
        for i, buy_price in enumerate(prices[:-1]):
            trade_profit = sorted(prices[i:], reverse=True)[0] - buy_price
            if trade_profit > profit:
                profit = trade_profit
                    
        return profit

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        profit = 0
        
        if prices:            
            buy_price = prices[0]

            for price in prices[1:]:
                trade_profit = price - buy_price

                if price < buy_price:
                    buy_price = price

                elif trade_profit > profit:
                    profit = trade_profit
                            
        return profit