serializeTree<T> function

String serializeTree<T>(BinaryTreeNode<T>? root)

Serializes a binary tree to a string representation

Uses level-order traversal with "null" for missing nodes. The format is: "value1,value2,null,value3,..."

Implementation

String serializeTree<T>(BinaryTreeNode<T>? root) {
  if (root == null) return "";

  final List<String> result = [];
  final List<BinaryTreeNode<T>?> queue = [root];

  while (queue.isNotEmpty) {
    final BinaryTreeNode<T>? node = queue.removeAt(0);

    if (node == null) {
      result.add("null");
    } else {
      result.add(node.value.toString());
      queue.add(node.left);
      queue.add(node.right);
    }
  }

  // Remove trailing nulls
  while (result.isNotEmpty && result.last == "null") {
    result.removeLast();
  }

  return result.join(",");
}