Symmetric Tree

Problem Description

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

Example 1:

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

Example 2:

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

Constraints:

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

Solution (Go)

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func isSymmetric(root *TreeNode) bool {
	if root == nil {
		return true
	}
	return isSymmetricRec(root.Left, root.Right)
}

func isSymmetricRec(left *TreeNode, right *TreeNode) bool {
	if left == nil && right == nil {
		return true
	}
	if left == nil || right == nil {
		return false
	}
	if left.Val != right.Val {
		return false
	}
	return isSymmetricRec(left.Left, right.Right) && isSymmetricRec(left.Right, right.Left)
}