buy_and_sell.py

class Solution:


 """

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

        profit = [0]

        for i in range(len(prices)):
            for j in range(i + 1, len(prices)):
                pot_prof = prices[j] - prices[i]
                if pot_prof < 0:
                    continue
                profit.append(pot_prof)
        return max(profit)


 """





  def get_max_profit(stock_prices):
    if len(stock_prices) < 2:
        raise ValueError('Getting a profit requires at least 2 prices')

    # We'll greedily update min_price and max_profit, so we initialize
    # them to the first price and the first possible profit
    min_price  = stock_prices[0]
    max_profit = stock_prices[1] - stock_prices[0]

    # Start at the second (index 1) time
    # We can't sell at the first time, since we must buy first,
    # and we can't buy and sell at the same time!
    # If we started at index 0, we'd try to buy *and* sell at time 0.
    # This would give a profit of 0, which is a problem if our
    # max_profit is supposed to be *negative*--we'd return 0.
    for current_time in range(1, len(stock_prices)):
        current_price = stock_prices[current_time]

        # See what our profit would be if we bought at the
        # min price and sold at the current price
        potential_profit = current_price - min_price

        # Update max_profit if we can do better
        max_profit = max(max_profit, potential_profit)

        # Update min_price so it's always
        # the lowest price we've seen so far
        min_price  = min(min_price, current_price)

    return max_profit