public void link(Fibonaccinode y, Fibonaccinode x) {
     y.left.right = y.right;
        y.right.left = y.left;
        y.parent = x;
        if (x.child == null) {
            x.child = y;
            y.right = y;
            y.left = y;
        } else {
            y.left = x.child;
            y.right = x.child.right;
            x.child.right = y;
            y.right.left = y;
        }
        x.degree++;
        y.mark = false;
    }