Mirror-Image Tree

Easy

You are given the root of a binary tree. Check whether the tree looks the same as its reflection across a vertical line through the root. In other words, the root's left subtree must be a mirror copy of its right subtree: mirrored positions hold nodes with equal values, and wherever one side has no node, the other side has none either. Return True if the tree is symmetric and False otherwise. Try solving it both recursively and iteratively.

Example 1

root=tree_node([7, 5, 5, None, 8, 8]) → True

The left 5 has only a right child 8 and the right 5 has only a left child 8. They match in the mirror.

Example 2

root=tree_node([7, 5, 5, 8, None, 8]) → False

Both 8s are left children, so in the mirror one of them lands opposite an empty spot.

Example 3

root=tree_node([4]) → True

A single node is symmetric.

Constraints

1 ≤ number of nodes ≤ 1000
-100 ≤ Node.val ≤ 100

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Topics

Tree Depth-First Search Breadth-First Search Binary Tree

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Identical Trees Easy Tree Height Easy Nearest Leaf Depth Easy Leaf Path With a Given Total Easy Mirror the Tree Easy

Input

root=tree_node([7, 5, 5, None, 8, 8])

Expected

True

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