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

class Solution:
    # @param preorder, a list of integers
    # @param inorder, a list of integers
    # @return a tree node
    def buildTree(self, preorder, inorder):
        if len(preorder) == 0:
            return None
        if len(preorder) == 1:
            return TreeNode(preorder[0])
        root = TreeNode(preorder[0])
        index = inorder.index(root.val)
        root.left = self.buildTree(preorder[1 : index + 1], inorder[0 : index])
        root.right = self.buildTree(preorder[index + 1 : len(preorder)], inorder[index + 1 : len(inorder)])
        return root