| // -*- C++ -*- |
| |
| // Copyright (C) 2005, 2006 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 2, 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 COPYING. If not, write to |
| // the Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
| // MA 02111-1307, USA. |
| |
| // As a special exception, you may use this file as part of a free |
| // software library without restriction. Specifically, if other files |
| // instantiate templates or use macros or inline functions from this |
| // file, or you compile this file and link it with other files to |
| // produce an executable, this file does not by itself cause the |
| // resulting executable to be covered by the GNU General Public |
| // License. This exception does not however invalidate any other |
| // reasons why the executable file might be covered by the GNU General |
| // Public License. |
| |
| // 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 pb_ds; |
| |
| // 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::const_point_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; |
| } |
| |