剑指Offer-- 树的子结构

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）

递归python版：

# -*- 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):
        # write code here
        if pRoot1 is None or pRoot2 is None:
            return False
         
        cur1 = pRoot1
        cur2 = pRoot2
        res = False
        if cur1.val == cur2.val:
            res = self.istree1hastree2(cur1,cur2)
        if not res:
            res = self.HasSubtree(cur1.left, cur2)
        if not res:
            res = self.HasSubtree(cur1.right, cur2)
        return res
    def istree1hastree2(self, tree1, tree2):
        if tree2 is None:
            return True
        if tree1 is None:
            return False
        res1 = False
        res2 = False
        if tree1.val == tree2.val:
            res1 = self.istree1hastree2(tree1.left,tree2.left)
            res2 = self.istree1hastree2(tree1.right,tree2.right)
        return (res1 and res2)