Check Tree Symmetry | Dataford Interview Questions

Scribd can represent a topic hierarchy as a binary tree for a programming exercise. Write a function that determines whether the tree is symmetric around its center, meaning the left and right subtrees are mirror images.

Formal Specification

Implement is_symmetric(root), where root is either None or a nested dictionary with this structure:

value: an integer node value
left: another node dictionary or None
right: another node dictionary or None

Return True if the tree is symmetric and False otherwise. Two corresponding nodes must have equal values, and their children must appear in mirrored positions. An empty tree is symmetric.

Constraints

The tree contains at most 10^5 nodes.
Each value is an integer between -10^9 and 10^9.
Each child is either a valid node dictionary or None.
The input tree may be empty.

Function Signature

def is_symmetric(root):

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