What is the best strategy to buy and sell stock once?
You are given daily stock prices and must determine the maximum profit achievable with a single transaction. This tests your grasp of greedy algorithms and dynamic programming concepts.
Why Interviewers Ask This
This question assesses your ability to maintain state while iterating through data to find optimal solutions. Interviewers look for candidates who can recognize that tracking the minimum price seen so far is sufficient to calculate maximum profit. It demonstrates logical thinking and the capacity to simplify complex financial problems into linear scans.
How to Answer This Question
Begin by defining the goal: maximize the difference between selling and buying prices where sell date is after buy date. Explain the greedy approach of tracking the minimum price encountered so far. Calculate potential profit at each step by subtracting the minimum price from the current price. Update the maximum profit variable whenever a higher profit is found. Conclude with complexity analysis.
Key Points to Cover
- Greedy algorithm application
- Single pass iteration logic
- State management for minimum price
- Profit calculation mechanics
Sample Answer
The optimal strategy involves iterating through the price array once while maintaining a running minimum price. At each day, I calculate the profit if I were to sell today by subtracting the minimum price seen so far fro…
Common Mistakes to Avoid
- Attempting to buy and sell on the same day
- Using nested loops leading to O(n^2) complexity
- Failing to update the minimum price correctly
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