dsa3 min read
Design Hit Counter — Count Requests in Last 300 Seconds
Design a hit counter that counts hits in the last 5 minutes using a deque-based sliding window or circular buffer with O(1) amortised operations.
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dsa3 min read
Time Based Key-Value Store — Binary Search on Timestamps
Design a key-value store that returns values at or before a given timestamp. Uses a hashmap of sorted (timestamp, value) lists with binary search for O(log n) get.
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dsa3 min read
Design Search Autocomplete System — Trie with Frequency Ranking
Design a search autocomplete system that returns top 3 historical queries matching the current prefix, sorted by frequency then lexicographically. Uses a Trie with per-node frequency maps.
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dsa2 min read
Design Browser History — Stack-Based Navigation
Design a browser with visit, back, and forward navigation. Uses two stacks (or a doubly-ended array with pointer) for O(1) visit and O(steps) navigation.
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dsa2 min read
Design a Leaderboard — Score Tracking with Top K
Design a leaderboard that tracks player scores, supports score additions, top K sum queries, and player resets using a hashmap with sorted aggregation.
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