Best Time to Buy and Sell Stock
Given daily stock prices, find the largest profit from one buy followed by one later sell.
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Lesson notes
Try it before you watch
Restate the problem in your own words, list the edge cases, and sketch a solution with its running time. Then play the video and compare.
Reveal the key idea
Walk through the prices once, keeping the lowest price so far and the best difference between today's price and that minimum.
Pattern: Greedy & intervals. Make the locally best choice, usually after sorting, and argue why it never hurts later.
Complexity
| Measure | Bound |
|---|---|
| Time | O(n) |
| Extra space | O(1) |
Walkthroughs often start from a simpler approach first; aim to reach these bounds. New to Big-O? Read understanding algorithmic complexity.