```
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def isSubtree(self, s, t):
"""
:type s: TreeNode
:type t: TreeNode
:rtype: bool
"""
def check(s, t):
# helper function that does the actual subtree check
if (s is None) and (t is None):
return True
if (s is None) or (t is None):
return False
return (s.val == t.val and check(s.left, t.left) and check(s.right, t.right))
# need to do a pre-order traversal and do a check
# for every node we visit for the subtree
if not s:
# return False since None cannot contain a subtree
return
if check(s, t):
# we found a match
return True
if self.isSubtree(s.left, t) or self.isSubtree(s.right, t):
# a match was found
return True
return False
```