Case 1: Including Null Nodes

public int widthOfBinaryTree (TreeNode root)
{
    if (root == null)
        return 0;
    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);
    int max = 0;
    while (!queue.isEmpty()) {
        int size = queue.size();
        // Check if all nodes at this level are null
        boolean allNull = queue.stream().allMatch(Objects::isNull);
        // Calculate level size
        int levelSize = getLevelSize(queue);
        max = Math.max(max, levelSize);
        // Process nodes at the current level
        for (int i = 0; i < size; i++) {
            TreeNode node = queue.poll();
            if (node != null) {
                queue.offer(node.left);
                queue.offer(node.right);
            }
            else if (!allNull) {
             // Add placeholders for null nodes if there are non-null nodes
                queue.offer(null);
                queue.offer(null);
            }
        }
    }
    return max;
}

private int getLevelSize (Queue<TreeNode> queue)
{
    List<TreeNode> list = new ArrayList<>(queue); // Convert queue to list
    int left = 0;
    int right = list.size() - 1;
    // Trim nulls from both ends of the list
    while (left <= right && list.get(left) == null) {
        left++;
    }
    while (left <= right && list.get(right) == null) {
        right--;
    }
    // Width is the number of non-null positions
    return right - left + 1;
}

Case 2: Excluding Null Nodes

public int widthOfBinaryTree (TreeNode root)
{
    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);
    int max = Integer.MIN_VALUE;
    while (!queue.isEmpty()) {
        int size = queue.size();

        max = Math.max(max, size);
        for (int i = 0; i < size; i++) {
            TreeNode element = queue.poll();
            if (element.left != null) {
                queue.offer(element.left);
            }
            if (element.right != null) {
                queue.offer(element.right);
            }
        }
    }
    return max;
}