Symmetric Binary Tree Check

You are given a binary tree represented in level-order traversal. The tree nodes are provided as a sequence of values where the value null represents an absent node.

Your task is to determine if the tree is symmetric. A binary tree is symmetric if the left subtree is a mirror reflection of the right subtree. Formally, a tree is symmetric if for every node, the following condition holds:

\( \text{isMirror}(L,R) = (L.val = R.val) \land \text{isMirror}(L.left,R.right) \land \text{isMirror}(L.right,R.left) \)

Note: An empty tree is considered symmetric.

inputFormat

The input is read from standard input (stdin) as a single line containing space-separated tokens representing the level-order traversal of the binary tree. Each token is either an integer or the string null (without quotes) representing a missing node.

For example: 1 2 2 3 4 4 3

outputFormat

Print to standard output (stdout) a single line: true if the tree is symmetric, or false if it is not.

1 2 2 3 4 4 3

true