平衡二叉樹判定

1.

 int height(TreeNode root) {
        if (root == null) return 0;
        return Math.max(height(root.left), height(root.right)) + 1;
    }

    public boolean isBalanced(TreeNode root) {
        if (root == null) return true;
        return Math.abs(height(root.left) - height(root.right)) <= 1 && isBalanced(root.left) && isBalanced(root.right);
    }