572. Subtree of Another Tree-另一个树的子树

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node’s descendants. The tree s could also be considered as a subtree of itself.

Example 1:
Given tree s:

Given tree t:

Return true, because t has the same structure and node values with a subtree of s.
 

Example 2:
Given tree s:

Given tree t:

Return false.

Solution in python:

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isDentical(self, s, t):
        if not s and not t:
            return True
        elif (s and not t) or (not s and t):
            return False
        else:
            if s.val != t.val:
                return False
            else:
                return self.isDentical(s.left, t.left) and self.isDentical(s.right, t.right)
    def isSubtree(self, s: TreeNode, t: TreeNode) -> bool:
        if not s:
            return False
        elif self.isDentical(s, t):
            return True
        else:
            return self.isSubtree(s.left, t) or self.isSubtree(s.right, t)