private boolean isBalanced = true;    public boolean IsBalanced_Solution(TreeNode root) {        height(root);        return isBalanced;    }        public int height(TreeNode root) {        if(root == null || !isBalanced) return 0;        int left = height(root.left);        int right = height(root.right);        if(Math.abs(left-right)>1) isBalanced = false;        return 1+Math.max(left, right);    }