/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */

/* Ex.: update the N fields! */
link rotR(link h)
  { link x = h->l; h->l = x->r; x->r = h; 
    return x; }
link rotL(link h)
  { link x = h->r; h->r = x->l; x->l = h; 
    return x; }