dsa7 min read
Shortest Subarray with Sum At Least K — Monotonic Deque on Prefix Sums
Solve LeetCode 862 Shortest Subarray with Sum At Least K in O(n) using a monotonic increasing deque on prefix sums. A FAANG hard interview classic.
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dsa7 min read
Walls and Gates — Multi-Source BFS Queue from Every Gate at Once
Solve LeetCode 286 Walls and Gates with multi-source BFS from every gate using a deque queue in O(m times n). A FAANG grid traversal classic.
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dsa6 min read
Flatten Nested List Iterator — Stack-Based Lazy Traversal
Solve LeetCode 341 Flatten Nested List Iterator with a lazy stack-based approach in O(1) amortized hasNext and next. A FAANG design favorite at Google, Meta, and Amazon.
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dsa6 min read
Remove All Adjacent Duplicates in String II — Counter Stack Pattern
Solve LeetCode 1209 Remove All Adjacent Duplicates II in O(n) using a counter stack of (char, count) pairs. A FAANG-favorite stack twist asked at Google and Amazon.
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dsa7 min read
Design Hit Counter — Sliding Window Queue with 5-Minute Retention
Solve LeetCode 362 Design Hit Counter using a queue or fixed-size circular buffer for O(1) amortized hits and constant-time getHits. A FAANG system design favorite.
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