#include <stdio.h>
#include <stdlib.h>

struct node
{ int data;
  struct node * left, * right; };

struct node * constr_node(int d)
{ struct node * t = (struct node *)malloc(sizeof(struct node));
  t->data = d;
  t->left = NULL;
  t->right = NULL;
  return t; }

void print(struct node * t)
{ if (t == NULL)
    return;
  printf("(");
  print(t->left);
  printf(" %d ", t->data);
  print(t->right);
  printf(")"); }

void out_tree(struct node * t, int fd)
{ if (t == NULL)
    return;
  out_tree(t->left, fd);
  write(fd, & t->data, sizeof(t->data));
  out_tree(t->right, fd); }

struct node * insert(struct node * t, int d)
{ if (t == NULL)
    return constr_node(d);
  if (d < t->data)
    t->left = insert(t->left, d);
  else
    t->right = insert(t->right, d);
  return t; }

void shuffle(int * a, int N)
{ int i, r, t;
  for (i = 0; i < 2*N; i += 1)
  { r = random() % N;
    t = a[r];
    a[r] = a[0];
    a[0] = t; } }

int main(int argc, char * argv[])
{ int number, i, p, comma[2], commb[2];
  int * array;
  struct node * tree1 = NULL, * tree2 = NULL;
  if (argc != 2)
  { fprintf(stderr, "usage: %s number-of-numbers\n", argv[0]);
    exit(1); }
  number = atol(argv[1]);
  array = (int *) malloc(sizeof(int) * number);
  for (i = 0; i < number; i += 1)
    array[i] = i + 1;
  srandomdev();
  shuffle(array, number);
  for (i = 0; i < number; i += 1)
    tree1 = insert(tree1,array[i]);
  shuffle(array, number);
  array[2] = random() % 20;
  for (i = 0; i < number; i += 1)
    tree2 = insert(tree2,array[i]);
  print(tree1);
  printf("\n");
  print(tree2);
  printf("\n");

  pipe(comma);
  pipe(commb);
  p = fork();
  if (p == 0)
  { close(comma[0]);
    out_tree(tree1, comma[1]);
    close(comma[1]);
    exit(0); }
  p = fork();
  if (p == 0)
  { close(commb[0]);
    out_tree(tree2, commb[1]);
    close(commb[1]);
    exit(0); }

  close(comma[1]);
  close(commb[1]);
  while (1)
  { int n1, n2, r;
    r = read(comma[0], & n1, sizeof(n1));
    if (r == 0) break;
    r = read(commb[0], & n2, sizeof(n2));
    if (r == 0) break;
    printf("received %d and %d\n", n1, n2); } }