Amazon Software Engineer Intern interview questions

leetcode medium algorithm style question

I have a list of integers representing the stock prices in each day. Write a function that returns what days to buy the stock and what days to sell the stock to maximize profit. Initially you can only buy, you can choose to not buy any at all. You can only sell after having bought, and can only buy again after having sold. Try to get as close to O(n) time complexity as possible.