/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
typedef struct node *link;
struct node { Item item; link l, r };
link NEW(Item item, link l, link r)
  { link x = malloc(sizeof *x); 
    x->item = item; x->l = l; x->r = r;
    return x;
  }
link max(Item a[], int l, int r)
  { int m = (l+r)/2; Item u, v;
    link x = NEW(a[m], NULL, NULL);
    if (l == r) return x;
    x->l = max(a, l, m);
    x->r = max(a, m+1, r);
    u = x->l->item; v = x->r->item;
    if (u > v) 
      x->item = u; else x->item = v;
    return x;
  }