思路和依据前序遍历和中序遍历重建树的思路一样，复杂度也一致，代码如下：

class Solution(object):    def buildTree(self, inorder, postorder):        """        :type inorder: List[int]        :type postorder: List[int]        :rtype: TreeNode        """        if not inorder:            return None        length = len(inorder)        map = {}        for i in xrange(length):            map[inorder[i]] = i        return self.helper(postorder,0,length-1,0,length-1,map)                def helper(self,postorder,Istart,Iend,Pstart,Pend,map):        if Istart > Iend:            return None        node = TreeNode(postorder[Pend])        if Istart == Iend:            return node        index = map[node.val]        node.left = self.helper(postorder,Istart,index-1, Pstart,Pstart+index-Istart-1,map)        node.right = self.helper(postorder,index+1,Iend,Pstart+index-Istart,Pend-1,map)        return node