Description
Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center). Return true or false.
Examples
Input:
root = [1,2,2,3,4,4,3]Output:
trueExplanation:
Comparing left and right subtrees as mirrors: left child 2 matches right child 2, left's children [3,4] match right's children [4,3] in reverse order.
Input:
root = [1,2,2,null,3,null,3]Output:
falseExplanation:
The left subtree has structure [2, null, 3] while the right subtree has [2, null, 3]. For symmetry, the right should mirror as [2, 3, null], but both have right children only.
Input:
root = [1]Output:
trueExplanation:
With only a root node and no children, the tree trivially mirrors itself. Both the left and right subtrees are empty (null), which are identical.
Constraints
- •
The number of nodes in the tree is in the range [1, 1000] - •
-100 ≤ Node.val ≤ 100