0121.py

# Source: https://leetcode.com/problems/best-time-to-buy-and-sell-stock
# Title: Best Time to Buy and Sell Stock
# Difficulty: Easy
# Author: Mu Yang <http://muyang.pro>

################################################################################################################################
# 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 <= 10^5
#   0 <= prices[i] <= 10^4
#
################################################################################################################################

class Solution:
    def maxProfit(self, prices: List[int]) -> int:

        profit = 0
        min_price = prices[0]

        for price in prices[1:]:
            min_price = min(min_price, price)
            profit = max(profit, price-min_price)

        return profit