106. 從中序與後序遍歷序列構造二叉樹

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

class Solution:
    def buildTree(self, inorder, postorder):
        """
        :type inorder: List[int]
        :type postorder: List[int]
        :rtype: TreeNode
        """
        if postorer is not:
            return None
        root = TreeNode(postorer[-1])
        n = inorder.index(root.val)
        root.left = self.buildTree(inorder[:n], postorder[:n])
        root.right = self.buildTree(inorder[n+1:], postorder[n:-1])
        return root