LeetCode "Symmetric Tree"

class Solution {
 public:
     bool isSymmetric(TreeNode *pl, TreeNode *pr)
     {
         if (!pl && !pr) return true;
         if ((pl && !pr) || (!pl && pr)) return false;
         
         if (pl->val != pr->val) return false;
         return isSymmetric(pl->left, pr->right) && (isSymmetric(pl->right, pr->left));
     }
     bool isSymmetric(TreeNode *root) {
         if (!root || (!root->left && !root->right)) return true;
         if ((!root->left && root->right) || (root->left && !root->right)) return false;

         return isSymmetric(root->left, root->right);         
     }
 };