best_time_to_buy_and_sell_stock.py

# 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


class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        left = 0
        right = 1
        max_profit = 0
        while right < len(prices):
            if prices[left] < prices[right]:
                max_profit = max(max_profit, prices[right]-prices[left])
            else:
                left = right
            right += 1
        
        return max_profit