这道题给我的教训：别轻视递归。

题干：

代码：

int geiHeight(TreeNode* node){if(node == NULL)return 0;int leftHeight = getHeight(node -> left);if(leftHeight == -1) return -1;int rightHeight = getHeight(node -> right);if(rightHeight == -1) return -1;if(abs(leftHeight - rightHeight) > 1) return -1;return 1 + max(leftHeight, rightHeight);
}bool isBalanced(TreeNode* root){return getHeight(root) == -1 ? false : true;
}