Maximum Profit Stock Market Problem Algorithm

Maximum Profit Stock Market Problem Algorithm

Writing coding interview questions hasn't made me rich. Maybe trading Apple stocks will.
I have an array stock_prices_yesterday where:

The indices are the time in minutes past trade opening time, which was 9:30am local time.
The values are the price in dollars of Apple stock at that time.
For example, the stock cost $500 at 10:30am, so stock_prices_yesterday[60] = 500.

Write an efficient algorithm for computing the best profit I could have made from 1 purchase and 1 sale of 1 Apple stock yesterday.

No "shorting"—you must buy before you sell. You may not buy and sell in the same time step (at least 1 minute must pass).

#Solution

def max_profit(stock_prices_yesterday)
i = 0
global_max = stock_prices_yesterday[1] - stock_prices_yesterday[0]
	while i < stock_prices_yesterday.length - 1 do
		j = 1
		while j < (stock_prices_yesterday.length - i) do
			local_max = stock_prices_yesterday[i + j] - stock_prices_yesterday[i] 
			if local_max > global_max
				global_max = local_max
			end
		j += 1
		end
	i += 1
	end
global_max
end