function Serialize(pRoot, arr = []) {
      if (!pRoot) {
        arr.push('#');
      } else {
        arr.push(pRoot.val);
        Serialize(pRoot.left, arr)
        Serialize(pRoot.right, arr)
      }
      return arr.join(',');
    }

    function Deserialize(s) {
      if (!s) {
        return null;
      }
      return deserialize(s.split(','));
    }

    function deserialize(arr) {
      let node = null;
      const current = arr.shift();
      if (current !== '#') {
        node = { val: current }
        node.left = deserialize(arr);
        node.right = deserialize(arr);
      }
      return node;
    }