What is the best way to buy and sell stock for maximum profit?
Direct Answer
This classic problem requires finding the maximum profit achievable by buying and selling a stock once on different days. It tests greedy algorithms and single-pass iteration skills.
Why Interviewers Ask This
This question is designed to test a candidate's grasp of greedy strategies and dynamic programming concepts. Interviewers look for the ability to track the minimum price seen so far while calculating potential profits in a single pass. It reveals how well you can simplify complex financial scenarios into efficient code without unnecessary loops.
How to Answer This Question
Begin by defining the goal: maximize profit = max(price[j] - price[i]) where j > i. Explain the one-pass algorithm where you maintain a running minimum price and update the maximum profit at each step. Avoid nested loops by iterating through the list once. Discuss why this greedy approach works optimally for a single transaction scenario. Conclude with complexity analysis.
Key Points to Cover
- Single pass iteration
- Tracking minimum price
- Greedy strategy application
- O(n) time complexity
Sample Answer
The optimal solution involves a single pass through the prices array. I initialize a variable for the minimum price seen so far and another for the maximum profit. As I iterate through the prices, I update the minimum pr…
Common Mistakes to Avoid
- Using nested loops unnecessarily
- Failing to update minimum price correctly
- Ignoring the constraint that sell must happen after buy
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