Best Time to Buy and Sell Stock

Find the maximum profit from one buy and one sell given daily prices.

arrays sliding-window profit minimum-prefix

Write a function `max_profit(prices)` that takes a list of non-negative integers `prices` representing the stock price on each consecutive day. The function must return the maximum profit you can achieve by choosing a single day to buy one stock and selecting a different day, strictly after the buy day, to sell that stock. If no profit is possible, return `0`.

You may only complete one transaction (buy once and sell once). You must buy before you sell.

Examples are provided below to clarify the expected behavior.

Constraints

- `len(prices) >= 1`
- `0 <= prices[i] <= 10^5`
- The time complexity of the expected solution is O(n), with O(1) extra space.

Example

```python
>>> max_profit([7, 1, 5, 3, 6, 4])
5
>>> max_profit([7, 6, 4, 3, 1])
0
>>> max_profit([3, 3, 3])
0
```

10 points ~15 min

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Hints

Track the lowest price seen so far as you iterate through the list.

At each day, compute the potential profit if you sell that day (price - min_so_far) and update the best profit.

The answer must be zero if no profitable transaction exists.

Test Results

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