题目
Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false otherwise.
A subtree of a binary tree tree is a tree that consists of a node in tree and all of this node's descendants. The tree tree could also be considered as a subtree of itself.
Example 1:
![[leetcode] 572. Subtree of Another Tree](https://ctyun-collect-0531.gdoss.xstore.ctyun.cn/files/2023/07/20/eb7591ddfaa841bda995a0b6adf1c261.png "[leetcode] 572. Subtree of Another Tree")
Input: root = [3,4,5,1,2], subRoot = [4,1,2]
Output: true
Example 2:
![[leetcode] 572. Subtree of Another Tree](https://ctyun-collect-0531.gdoss.xstore.ctyun.cn/files/2023/07/20/1d00183bff5843ecbffb7e660135f119.png "[leetcode] 572. Subtree of Another Tree")
Input: root = [3,4,5,1,2,null,null,null,null,0], subRoot = [4,1,2]
Output: false
Constraints:
- The number of nodes in the
roottree is in the range[1, 2000]. - The number of nodes in the
subRoottree is in the range[1, 1000]. -104 <= root.val <= 104-104 <= subRoot.val <= 104
思路
递归，首先实现一个isEquals函数用来判断两棵树是否相等，然后将root树的每个节点都和subRoot树使用isEquals判断是否相等，并返回结果。
代码
python版本：
class Solution:
def isSubtree(self, root: Optional[TreeNode], subRoot: Optional[TreeNode]) -> bool:
def isEquals(root1, root2):
if not (root1 and root2):
return root1 is root2
return (root1.val == root2.val and isEquals(root1.left, root2.left) and isEquals(root1.right, root2.right))
if isEquals(root, subRoot):
return True
if not root:
return False
return self.isSubtree(root.left, subRoot) or self.isSubtree(root.right, subRoot)
