public static ArrayList<String> serializeTree(TreeNode tree) {
ArrayList<String> res = new ArrayList<>();
LinkedList<TreeNode> queue = new LinkedList<>();
queue.addLast(tree);
while (!queue.isEmpty()) {
TreeNode node = queue.removeFirst();
if (node == null) {
res.add(NULL);
} else {
res.add(String.valueOf(node.val));
queue.add(node.left);
queue.add(node.right);
}
}
while (res.size() > 1 && res.get(res.size() - 1).equals(NULL)) {
res.remove(res.size() - 1);
}
return res;
}
public static TreeNode createTree(ArrayList<String> list) {
LinkedList<NodeWithBranch> queue = new LinkedList<>();
TreeNode head = new TreeNode(0);
queue.addLast(new NodeWithBranch(head, 0));
for (String s : list) {
NodeWithBranch node = queue.removeFirst();
if (!s.equals(NULL)) {
if (node.branch == 0) {
node.tree.left = new TreeNode(Integer.parseInt(s));
queue.addLast(new NodeWithBranch(node.tree.left, 0));
queue.addLast(new NodeWithBranch(node.tree.left, 1));
} else {
node.tree.right = new TreeNode(Integer.parseInt(s));
queue.addLast(new NodeWithBranch(node.tree.right, 0));
queue.addLast(new NodeWithBranch(node.tree.right, 1));
}
}
}
return head.left;
}