Vertical Order Traversal

Short summary

Solve binary tree vertical order traversal in O(N log N) using BFS with (row, column) coordinates tracked via nested TreeMaps and PriorityQueues. Groups nodes by column, sorts rows within each column, then extracts values in order.

• •Use BFS to assign each node a (row, column) coordinate pair
• •Store in TreeMap<Column, TreeMap<Row, PriorityQueue>> for automatic nested sorting
• •Extract columns left-to-right, rows top-to-bottom, values by priority—O(N log N) time, O(N) space

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