二叉树子树

leetcode572
问题：判断t是否为s的子树

python解决方案
class TreeNode:
	def __init__(self):
    self.val = val
    self.left = None
    self.right = None
class Solution:
	def isSubtitle(t,s):
    def up(t):
    	return (t.val, up(t.left), up(t.right)) if t else None
    return str(up(t))  in str(up(s))

注意点：

• 元组中的元素位置不会发生变化
• print(“a” in “ab”) 返回true