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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2009 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 basic_multimap_example.cpp

 * A basic example showing how to use multimaps.

 */

/**

 * This example shows how to use "multimaps" in the context of a simple

 * bank account application. Each customer holds a bank account

 * (or more than one) which holds some balance.

 */

#include <iostream>

#include <string>

#include <cassert>

#include <ext/pb_ds/assoc_container.hpp>

using namespace std;

using namespace __gnu_pbds;

// A simple hash functor.

// hash could serve instead of this functor, but it is not yet

// standard everywhere.

struct string_hash : public unary_function<string, size_t>

{

  inline size_t

  operator()(const string& r_s) const

  {

    size_t ret = 0;

    string::const_iterator b = r_s.begin();

    string::const_iterator e = r_s.end();

    while (b != e)

      {

        ret *= 5;

        ret += static_cast<size_t>(*(b++));

      }

    return ret;

  }

};

int main()

{

  // Each customer is identified by a string.

  typedef string customer;

  // Each account is identified by an unsigned long.

  typedef unsigned long account_id;

  // The balance in the account is a floating point.

  typedef float balance_t;

  /*

   *  This is the data structure type used for storing information

   *  about accounts. In this case the primary key is the customer,

   *  and the secondary key is the account id.

   *

   *  A hash-based container maps each customer to a list-based

   *  container that maps each account to the balance it holds.

   *

   *  Note that we could use any combination of primary and secondary

   *  associative-containers. In this case we choose a hash-based

   *  container for the primary keys, since we do not need to store

   *  customers in a sorted order; we choos a list-based container for

   *  the secondary keys, since we expect that the average number of

   *  accounts per customer will be small.

   */

  typedef

    cc_hash_table<

    customer,

    list_update<

    account_id,

    balance_t>,

    string_hash>

    accounts_t;

  // This object will hold all information.

  accounts_t acc;

  // Customer "a" opens empty account 12.

  acc["a"][12] = 0;

  // Customer "a" deposits 45 into account 12.

  acc["a"][12] += 45;

  // Customer "b" opens account 13 with balance 12.3.

  acc["b"][13] = 12.3;

  // Customer "c" opens empty account 14.

  acc["c"][14] = 0;

  // Customer "a" opens account 160 with balance 142.

  // Note that "a" already holds account 12.

  acc["a"][160] = 142;

  // Verify the number of accounts that "a" holds.

  accounts_t::point_const_iterator it = acc.find("a");

  assert(it != acc.end());

  assert(it->second.size() == 2);

  // The begining of the month has arrived. We need to give a 3%

  // interest to all accounts with a positive balance.

  // First we loop over all customers.

  accounts_t::iterator cust_it;

  for (cust_it = acc.begin(); cust_it != acc.end(); ++cust_it)

    {

      // For each customer, we loop over the customer's accounts.

      accounts_t::mapped_type::iterator it;

      for (it = cust_it->second.begin(); it != cust_it->second.end(); ++it)

        if (it->second > 0)

          it->second *= 1.03;

    }

  // Customer "a" closes all accounts.

  acc.erase("a");

  // The bank now has only 2 customers.

  assert(acc.size() == 2);

  return 0;

}