Solution: Vertical Order Traversal of a Binary Tree

Statement

Given the root of a binary tree, return the vertical order traversal of its nodes' values.

The nodes should be grouped into columns based on their horizontal position in the tree:

• The root is at column 0.

• The left child of a node is one column to the left of its parent.

• The right child of a node is one column to the right of its parent.

• Return the columns from the leftmost column to the rightmost column.

• Within each column, return nodes from top to bottom.

• If two nodes have the same row and column, they should appear from left to right.

Constraints:

• The number of nodes in the tree is in the range [0, 100].

• $-100 ≤$ Node.val $≤ 100$ ...