Given a binary tree, write a function to get 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 right most non-null nodes in the level, where the null nodes between the end-nodes are also counted into the length calculation. It is guaranteed that the answer will in the range of 32-bit signed integer. Example 1: Input: 1 / \ 3 2 / \ \ 5 3 9 Output: 4 Explanation: The maximum width existing in the third level with the length 4 (5,3,null,9). Example 2: Input: 1 / 3 / \ 5 3 Output: 2 Explanation: The maximum width existing in the third level with the length 2 (5,3). Example 3: Input: 1 / \ 3 2 / 5 Output: 2 Explanation: The maximum width existing in the second level with the length 2 (3,2). Example 4: Input: 1 / \ 3 2 / \ 5 9 / \ 6 7 Output: 8 Explanation:The maximum width existing in the fourth level with the length 8 (6,null,null,null,null,null,null,7). Constraints: The given binary tree will have between 1 and 3000 nodes.