private void markst(Subre t) {
        assert t != null;

        t.flags |= Subre.INUSE;
        if (t.left != null) {
            markst(t.left);
        }
        if (t.right != null) {
            markst(t.right);
        }
    }
private void markst(Subre t) {
        assert t != null;

        t.flags |= Subre.INUSE;
        if (t.left != null) {
            markst(t.left);
        }
        if (t.right != null) {
            markst(t.right);
        }
    }
private void markst ( Subre t ) { assert t != null ; t . flags |= Subre . INUSE ; if ( t . left != null ) { markst ( t . left ) ; } if ( t . right != null ) { markst ( t . right ) ; } }
markst - mark tree nodes as INUSE
markst - mark tree nodes as INUSE