二叉树相关操作

public static TreeNode stringToTreeNode(String input) {
    input = input.trim();
    if (input.length() == 0) {
        return null;
    }
    String[] parts = input.split(",");
    String item = parts[0];
    TreeNode root = new TreeNode(Integer.parseInt(item));
    Queue<TreeNode> nodeQueue = new LinkedList<>();
    nodeQueue.add(root);
    int index = 1;
    while(!nodeQueue.isEmpty()) {
        TreeNode node = nodeQueue.remove();

        if (index == parts.length) {
            break;
        }

        item = parts[index++];
        item = item.trim();
        if (!item.equals("null")) {
            int leftNumber = Integer.parseInt(item);
            node.left = new TreeNode(leftNumber);
            nodeQueue.add(node.left);
        }

        if (index == parts.length) {
            break;
        }

        item = parts[index++];
        item = item.trim();
        if (!item.equals("null")) {
            int rightNumber = Integer.parseInt(item);
            node.right = new TreeNode(rightNumber);
            nodeQueue.add(node.right);
        }
    }
    return root;
}