[LinkedIn]Serialize and deserialize a binary tree

From Here
Assume we have a binary tree below:

    _30_ 
   /    \    
  10    20
 /     /  \ 
50    45  35

Using pre-order traversal, the algorithm should write the following to a file:

30 10 50 # # # 20 45 # # 35 # #

/*SERIALIZE: The pre-order traversal code below does all the job to serialize a binary tree, believe it or not!*/

void writeBinaryTree(BinaryTree *p, ostream &out) {
  if (!p) {
    out << "# ";
  } else {
    out << p->data << " ";
    writeBinaryTree(p->left, out);
    writeBinaryTree(p->right, out);
  }
}

//deserialize
void readBinaryTree(BinaryTree *&p, ifstream &fin) {
  int token;
  bool isNumber;
  if (!readNextToken(token, fin, isNumber)) 
    return;
  if (isNumber) {
    p = new BinaryTree(token);
    readBinaryTree(p->left, fin);
    readBinaryTree(p->right, fin);
  }
}