문제

리트코드 121. Best Time to Buy and Sell Stock
난이도: ⭐

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.
(한 번의 거래로 낼 수 있는 최대 이익을 산출하라.)

예시 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.

예시 2

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

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나의 풀이:

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        min_price = sys.maxsize
        max_profit = -sys.maxsize
        
        for i in range(len(prices)):
            if prices[i] <= min_price:
                min_price = prices[i]
                
            if prices[i] - min_price >= max_profit:
                max_profit = prices[i] - min_price
        
        return max_profit

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# 더 나은 코드
class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        min_price = sys.maxsize
        profit = 0
        
        for price in prices:
            min_price = min(min_price, price)
            profit = max(price-min_price, profit)
        
        return profit