[leetcode] Symmetric Tree

public class Solution {

    public boolean isSymmetric(TreeNode root) {
        if (root == null)
            return true;
        return check(root.left, root.right);
    }

    private boolean check(TreeNode left, TreeNode right) {
        if (left == null && right == null)
            return true;
        if (left == null || right == null)
            return false;
        if (left.val != right.val)
            return false;
        return check(left.right, right.left) && check(left.left, right.right);

    }

    public static void main(String[] args) {
        TreeNode root = new TreeNode(10);
        root.left = new TreeNode(5);
        root.left.right = new TreeNode(9);
        root.right = new TreeNode(5);
        root.right.left = new TreeNode(9);

        System.out.println(new Solution().isSymmetric(root));

    }

}