121. Best Time to Buy and Sell Stock - Leetcode Python Solution

 121. Best Time to Buy and Sell Stock

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

In [ ]:

from typing import List
class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        max_profit = 0
        min_num = prices[0]
        for i in range (1,len(prices)):
          if prices[i]<min_num:
            min_num=prices[i]
          profit = prices[i] - min_num
          if max_profit<profit:
            max_profit=profit
        return max_profit

s = Solution()
s.maxProfit([7,6,4,3,1])

Out[ ]:

0