Maximum Binary Tree

给一个数组, 求返回mbt, 定义mbt是

  1. Create a root node whose value is the maximum value in nums.
  2. Recursively build the left subtree on the subarray prefix to the left of the maximum value.
  3. Recursively build the right subtree on the subarray suffix to the right of the maximum value.

这个题直接找max的index就可以.