Mirror the Tree

Easy

You are given the root of a binary tree. Turn it into its mirror image: at every node, the left and right subtrees trade places. Return the root of the resulting tree. If the tree is empty, return None.

Example 1

root=tree_node([10, 5, 20, 3, None, 15]) → [10, 20, 5, None, 15, None, 3]

Every node swaps its left and right subtrees: 20 moves to the left, 5 to the right, and 3 and 15 switch sides under their parents.

Example 2

root=tree_node([1, None, 2]) → [1, 2]

The only right child becomes a left child.

Example 3

root=tree_node([]) → None

An empty tree has nothing to mirror.

Constraints

0 ≤ number of nodes ≤ 100
-100 ≤ Node.val ≤ 100

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Topics

Tree Depth-First Search Breadth-First Search Binary Tree

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Input

root=tree_node([10, 5, 20, 3, None, 15])

Expected

[10, 20, 5, None, 15, None, 3]

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