在树中查找子树的简便方法

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def find_subtree(root, sub_root):
    if root is None:
        return False
    if is_same_tree(root, sub_root):
        return True
    return find_subtree(root.left, sub_root) or find_subtree(root.right, sub_root)

def is_same_tree(p, q):
    if p is None and q is None:
        return True
    if p is None or q is None:
        return False
    if p.val != q.val:
        return False
    return is_same_tree(p.left, q.left) and is_same_tree(p.right, q.right)