输入两棵二叉树A，B，判断B是不是A的子结构。（ps：我们约定空树不是任意一个树的子结构）

subsettree.py

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def HasSubtree(self, pRoot1, pRoot2):
        if pRoot2 is None:
            return False
        rst1=[]
        rst2=[]
        self.pre(pRoot1,rst1)
        self.pre(pRoot2,rst2)
        return set(rst2).issubset(rst1)
        # write code here
    def pre(self,tree,rst):
        if tree is None:
            return
        rst.append(tree.val)
        self.pre(tree.left,rst)
        self.pre(tree.right,rst)