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Best Time to Buy and Sell Stock
Best Time to Buy and Sell Stock is the sliding window pattern: grow, shrink, and maintain just enough state to stay linear. It's a great warm-up that builds stateful scanning without a ton of moving parts. The trap is updating window state in the wrong order when you expand or shrink.
Learn this pattern
Arrays and Hashing Interview Questions
Arrays and hashing problems are about fast lookup choices: set for membership, map for attached state, and buckets when counts are bounded. Reach for this family when brute force compares too many pairs or when you need to remember what you saw earlier in one pass.
Meet your coaches
Talk through the problem while you code. Signed-in reps become prep memory for the next session.
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Arrays and Hashing Interview Questions gives you a useful next rep while you are still on your phone.