/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
link rotR(link h)
  { link x = h->l; h->l = x->r; x->r = h;
    h->N = h->l->N + h->r->N + 1;
    x->N = x->l->N + x->r->N + 1;
    return x; }

link rotL(link h)
  { link x = h->r; h->r = x->l; x->l = h;
    h->N = h->l->N + h->r->N + 1;
    x->N = x->l->N + x->r->N + 1;
    return x; }