100.相同的树

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        # 如果两棵树都不存在，返回True
        if p is None and q is None:
            return True
        
        # 如果两棵树都存在
        if p is not None and q is not None:
            return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
        
        # 一棵树存在一棵树不存在
        return False