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LeetCode 239 Sliding Window Maximum is a Google classic that returns the max of every length-k window. The optimal answer maintains a monotonic decreasing deque of indices for amortised O(n) time.
LeetCode 76 Minimum Window Substring is a Google staple solved with a two-pointer sliding window plus a need-and-have frequency counter. Optimal solution runs in O(n + m) time and O(m) space.
Implement a lazy iterator over a nested integer list using a stack. Meta frequently tests this to evaluate iterator design, lazy evaluation, and stack-based tree traversal.
Encode a binary tree to a string and reconstruct it. Meta ranks this as their number-one tree interview question, testing BFS level-order traversal and string parsing under pressure.
Implement a read() function using a read4() primitive that reads exactly 4 characters at a time. Meta uses this to test buffer management, pointer arithmetic, and state machine design for file I/O.