Print offer binary tree from top to bottom to prove safety

          vector<TreeNode*> data;
          vector<int> result;
          data.push_back(root);
          if (root == nullptr) return result;
          while (!data.empty()){
              TreeNode *temp = data[0];
              result.push_back(temp->val);
              data.erase(data.begin());
              if(temp->left){
                  data.push_back(temp->left);
              }
              if(temp->right){
                  data.push_back(temp->right);
              }
          }
        return result;