对称的二叉树

/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    boolean isSymmetrical(TreeNode pRoot) {
        if (pRoot == null || (pRoot.left == null && pRoot.right == null))
            return true;
        
        return mirror(pRoot.left, pRoot.right);
    }
    
    boolean mirror(TreeNode node1, TreeNode node2) {
        if (node1 == null && node2 == null)
            return true;
        if (node1 != null && node2 != null) {
            return node1.val == node2.val && mirror(node1.left, node2.right) && mirror(node1.right, node2.left);
        }
        return false;
    }
    
    
}