Group a tree by vertical columns
Company: Meta
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
Given the root of a binary tree, produce a vertical listing of nodes: assign each node an x-coordinate (root at x=0; left child x−1; right child x+
1). For each x from smallest to largest, list node values from top to bottom; when multiple nodes share the same (x, depth), order them by their left-to-right appearance in level order. Return a list of columns (each a list of values). Describe your traversal strategy, tie-breaking, and data structures. Analyze time and space complexity.
Quick Answer: This question evaluates understanding of binary tree traversal, spatial coordinate mapping, ordering and tie-breaking rules, and the use of auxiliary data structures to group nodes by vertical columns.