boolean isSymmetrical(TreeNode pRoot) {
if (pRoot == null)
return true;
return isSymmetrical(pRoot.left, pRoot.right);
}
boolean isSymmetrical(TreeNode t1, TreeNode t2) {
if (t1 == null && t2 == null)
return true;
if (t1 == null || t2 == null)
return false;
if (t1.val != t2.val)
return false;
return isSymmetrical(t1.left, t2.right) && isSymmetrical(t1.right, t2.left);
}