Given the `root` of a binary tree, return the maximum width of the given tree.

The maximum width of a tree is the maximum width among all levels.

The width of one level is defined as the length between the end-nodes (the leftmost and rightmost non-null nodes), where the null nodes between the end-nodes that would be present in a complete binary tree extending down to that level are also counted into the length calculation.

It is guaranteed that the answer will in the range of a 32-bit signed integer.

Example 1:

    Input: root = [1,3,2,5,3,null,9]
    Output: 4
    Explanation: The maximum width exists in the third level with length 4 (5,3,null,9).

Example 2:

    Input: root = [1,3,2,5,null,null,9,6,null,7]
    Output: 7
    Explanation: The maximum width exists in the fourth level with length 7 (6,null,null,null,null,null,7).

Example 3:

    Input: root = [1,3,2,5]
    Output: 2
    Explanation: The maximum width exists in the second level with length 2 (3,2).

Constraints:

- The number of nodes in the tree is in the range `[1, 3000]`.
- `-100 <= Node.val <= 100`