libstdc++-v3/testsuite/ext/pb_ds/example/tree_join.cc

// -*- C++ -*-

// Copyright (C) 2005-2023 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
// Foundation; either version 3, or (at your option) any later
// version.

// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this library; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.


// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice
// and this permission notice appear in supporting documentation. None
// of the above authors, nor IBM Haifa Research Laboratories, make any
// representation about the suitability of this software for any
// purpose. It is provided "as is" without express or implied
// warranty.

/**
 * @file tree_join_example.cpp
 * An example showing how to join splay_tree_map objects.
 *    The code in the example is relevant to red-black trees as well.
 */

/**
 * This example shows how to join tree based containers, i.e., taking two
 *     objects with non-overlapping sets of keys and combining them into
 *    a single object.
 */

// For tree
#include <ext/pb_ds/assoc_container.hpp>
// For join_error exception.
#include <ext/pb_ds/exception.hpp>
// For assert
#include <cassert>

using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_pbds;

int main()
{
  /*
   *  
   */
  // A splay tree table mapping ints to chars.
  typedef tree<int, char, less<int>, splay_tree_tag> map_t;

  // Two map_t object.
  map_t h0, h1;

  // Insert some values into the first table.
  for (int i0 = 0; i0 < 100; ++i0)
    h0.insert(make_pair(i0, 'a'));

  // Insert some values into the second table.
  for (int i1 = 0; i1 < 100; ++i1)
    h1.insert(make_pair(1000 + i1, 'b'));

  // Since all the elements in h0 are smaller than those in h1, it is
  // possible to join the two tables. This is exception free.
  h0.join(h1);

  // Check that h0 should now contain all entries, and h1 should be empty.
  assert(h0.size() == 200);
  assert(h1.empty());


  // Two other map_t objects.
  map_t h2, h3;

  h2[1] = 'a';
  h2[3] = 'c';

  h3[2] = 'b';

  // Now perform an illegal join.
  // It is not true that all elements in h2 are smaller than those in
  // h3, nor is it true that they are all larger. Hence, attempting to
  // join h2, and h3 should result in an exception.
  bool exception_thrown = false;
  try
    {
      h2.join(h3);
    }
  catch (__gnu_pbds::join_error& )
    {
      exception_thrown = true;
    }
  assert(exception_thrown);

  // Since the operation was not performed, the tables should be unaltered.
  assert(h2.size() == 2);
  assert(h3[2] == 'b');

  return 0;
}