判断根结点是否等于子结点之和

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示例代码：

# 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 checkTree(self, root: Optional[TreeNode]) -> bool:
        return root.val == root.left.val + root.right.val

示例代码2：

# 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 checkTree(self, root: Optional[TreeNode]) -> bool:
        if not root:
            return True # 空树满足条件
        
        def is_sum_equal(node):
            if not node:
                return False
            
            if node.left and node.right:
                return node.val == node.left.val + node.right.val
            elif node.left:
                return node.val == node.left.val
            elif node.right:
                return node.val == node.right.val
            else:
                return True # 叶子节点满足条件
        return is_sum_equal(root) and self.checkTree(root.left) and self.checkTree(root.right)