怎么判断平衡二叉树

bool isBalanced(TreeNode *root, int &height)
{
    if(!root) return true;
    int left=0,right=0;
    if(!isBalanced(root->left,left)) return false;
    if(!isBalanced(root->right,right)) return false;
    if(abs(left-right) > 1) return false;
    height = max(left,right) + 1;
    return true;
}