662. Maximum Width of Binary Tree

题目

Given a binary tree, write a function to get the maximum width of the given tree. The width of a tree is the maximum width among all levels. The binary tree has the same structure as a full binary tree, but some nodes are null.

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.

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).

Note: Answer will in the range of 32-bit signed integer.

解题思路

见程序注释