Symmetric Tree

Symmetric Tree

Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Examples

Example 1:

Input: root = [1, 2, 2, 3, 4, 4, 3]
Output: true

        1
       / \
      2   2
     / \ / \
    3  4 4  3

Example 2:

Input: root = [1, 2, 2, null, 3, null, 3]
Output: false

      1
     / \
    2   2
     \   \
      3   3

Constraints

• The number of nodes in the tree is in the range [1, 1000].
• -100 <= Node.val <= 100

Expected Complexity

• Time: O(n)
• Space: O(h) where h is the height of the tree