OFF28 对称二叉树

public boolean isSymmetric(TreeNode root) {
        if(root == null){
            return true;
        }
        return judge(root.left,root.right); 
    }
    //左节点的left = 右节点的right  左节点的right = 右节点的left
    boolean judge(TreeNode L, TreeNode R) {
        if(L == null && R == null) return true;
        if(L == null || R == null || L.val != R.val) return false;
        return judge(L.left, R.right) && judge(L.right, R.left);
    }