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; }
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; }