题目描述：
给定两个二叉树，编写一个函数来检验它们是否相同。
如果两个树在结构上相同，并且节点具有相同的值，则认为它们是相同的。
解法1：
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def isSameTree(self, p, q):
"""
:type p: TreeNode
:type q: TreeNode
:rtype: bool
"""
if p is None and q is None:
return True
elif p is not None and q is not None:
if p.val==q.val:
return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
else:
return False
else:
return False