Construct Binary Tree from Inorder and Postorder Traversal

Given inorder and postorder traversal of a tree, construct the binary tree.

Note: You may assume that duplicates do not exist in the tree.

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def buildTree(self, inorder, postorder):
        """
        :type inorder: List[int]
        :type postorder: List[int]
        :rtype: TreeNode
        """
        return self.create_tree(inorder, 0, len(inorder) -1 , postorder, 0, len(postorder) - 1)


    def search_divindex(self, inorder, low_inorder, high_inorder, val):
        for i in range(low_inorder, high_inorder+1):
            if inorder[i] == val:
                return i
        return -1

    def create_tree(self, inorder, low_inorder, high_inorder, postorder, low_postorder, high_postorder):
        if (low_inorder > high_inorder) or (low_postorder > high_postorder):
            return None
        root = TreeNode(postorder[high_postorder])

        div_index = self.search_divindex(inorder, low_inorder, high_inorder, root.val)

        size_left_subtree = div_index - low_inorder
        size_right_subtree = high_inorder - div_index

        root.right = self.create_tree(inorder, div_index + 1, high_inorder, postorder, 
                                      high_postorder - size_right_subtree, high_postorder - 1)

        root.left = self.create_tree(inorder, low_inorder, div_index - 1,
                                     postorder,
                                     high_postorder - size_right_subtree - size_left_subtree,
                                     high_postorder - size_right_subtree - 1)

        return root