dsa2 min read
Meta — Flatten Nested List Iterator (Stack-Based)
Implement an iterator for a nested list that flattens it lazily. Meta favors this for testing iterator design, stack usage, and lazy evaluation.
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dsa2 min read
Meta — Serialize and Deserialize Binary Tree (BFS/Preorder)
Serialize a binary tree to a string and deserialize it back. Meta loves this problem for testing tree traversal and string parsing. Both BFS and preorder DFS approaches shown.
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dsa2 min read
Meta — Read N Characters Given read4 (Buffered Read)
Implement a read() function using a read4() primitive. Two variants: read once and read multiple times. Tests buffer management and pointer arithmetic.
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dsa3 min read
Amazon — Number of Islands II (Union-Find Dynamic)
Count islands after each addLand operation using incremental Union-Find. Each new land cell potentially merges with up to 4 neighbors — classic Amazon system-at-scale problem.
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dsa2 min read
Amazon — Kth Largest Element in a Stream (Min-Heap)
Design a stream that always returns the kth largest element after each add. Uses a min-heap of size k — the top is always the kth largest.
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