lc110.平衡二叉树

# 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 isBalanced(self, root: TreeNode) -> bool:

        def dfs(node):
            if not node:
                return 0
            left = dfs(node.left)
            if left == -1:
                return -1
            right = dfs(node.right)
            if right == -1:
                return -1
            return max(left, right) + 1 if abs(left - right) <= 1 else -1
        return dfs(root) != -1