prg10_5.cpp

这是数据结构和算法的国外经典书籍.清华大学出版社出版的<数据结构C++语言描述-应用模板库STL>陈君 译 英文名称是Data Structures with C++ Using STL.

// File: prg10_5.cpp
// the program simulates inventory maintenance for a
// video store. the program stores the title of a film
// and the number of copies the store owns in a video
// object. the video class has functions that access
// and update the number of copies, compare objects
// by title, and output a title and the number of copies.
// the function setupInventory() inputs film titles
// from the file "films.dat" and creates the stree
// object inventory of video data. after listing the
// films in the inventory, in an interactive loop
// the clerk inputs whether the customer wishes
// to rent a film, return a film, or whether business
// is over for the day. when a customer rents a film,
// the program updates the inventory by reducing the
// number of copies of the film by 1, and adds the film
// to the stree object rentals that maintains a database
// of rented films. when a customer returns a film, the
// program removes 1 copy of the film from the rentals
// object and increases the number of copies in inventory
// by 1. at the end of the business day, the program outputs
// the list of rented films and the films remaining in
// the inventory

#include <iostream>
#include <fstream>
#include <string>
#include <utility>		// for pair class

#include "d_stree.h"		// stree class
#include "d_video.h"		// video class
#include "d_util.h"		// for writeSTree()

using namespace std;

// initialize inventoryList from file "films.dat"
void setupInventory(stree<video>& inventory);

// process the return of a film
void returnTransaction(stree<video>& inventory,
			  stree<video>& rentals, const string& filmName);

// process the rental of a film
void rentalTransaction(stree<video>& inventory,
			  stree<video>& rentals, const string& filmName);

int main()
{
	// the inventory and rental lists
	stree<video> inventory, rentals;
	// assign return value from find() to filmIter
	stree<video>::iterator filmIter;
	// input from store operator. transactionType = "Rent", "Return",
	// or "Done"
	string transactionType;

	// film requested by a customer
	string filmName;

	// read and output inventory file
	setupInventory(inventory);
	cout << "Initial inventory list:" << endl;
	writeSTree(inventory, "\n");
	cout << endl;

	// process customers by entering "Rental" or "Return"
	// followed by the film name or "Done" to end the program.
	// for "Rent", decrease number of copies in inventory by 1
	// and add the copy to the rental database. for "Return",
	// remove copy from rental database and increase number
	// of copies in inventory by 1
	cout << "Transactions: Enter type (Rent, Return, Done)" << endl;
	cout << "followed by film name or space if done" << endl << endl;
	while (true)
	{
		// input the transaction type. the input must terminate with
		// a blank
		cout << "Transaction: ";
		getline(cin, transactionType, ' ');
		// if "Done", terminate the loop
		if (transactionType == "Done")
			break;

		// get film name
		getline(cin, filmName,'\n');

		if (transactionType == "Return")
			returnTransaction(inventory, rentals, filmName);
		else
			rentalTransaction(inventory, rentals, filmName);
	}
	cout << endl;

	// output the final rental and inventory lists.
	cout << "Rented Films: " << endl << endl;
	writeSTree(rentals, "\n");
	cout << endl;
	cout << "Films Remaining in Inventory:" << endl << endl;
	writeSTree(inventory, "\n");

	return 0;
}

void setupInventory(stree<video>& inventory)
{
	ifstream filmFile;	// input stream
	string filmName;		// individual file names
	// use with stree insert()
	pair<stree<video>::iterator, bool> p;

	// open the file "films.dat"
	filmFile.open("films.dat");
	if (!filmFile)
	{
		cerr << "File 'films.dat' not found!" << endl;
		exit(1);
	}

	// read lines until EOF; insert names in inventory list
	while(true)
	{
		getline(filmFile,filmName,'\n');
		if (!filmFile)
			break;

		// try an insertion with default of 1 copy
		p = inventory.insert(video(filmName));
		// see if video already in the inventory
		if (p.second == false)
			// it is in the inventory. increment number of copies
			(*(p.first)).updateCopies(1);
	}
}

void returnTransaction(stree<video>& inventory,
			  stree<video>& rentals, const string& filmName)
{
	stree<video>::iterator filmIter;

	// locate the film in the return database
	filmIter = rentals.find(video(filmName));
	// if there is only 1 copy left, erase the entry;
	// otherwise, decrease the number of rented copies
	// by 1
	if ((*filmIter).getCopies() == 1)
		rentals.erase(filmIter);
	else
		(*filmIter).updateCopies(-1);

	// locate the film in the inventory and increase the
	// number of copies available by 1
	filmIter = inventory.find(video(filmName));
	(*filmIter).updateCopies(1);

}

void rentalTransaction(stree<video>& inventory,
			  stree<video>& rentals, const string& filmName)
{
	stree<video>::iterator filmIter;
	// use pObj with stree insert()
	pair<stree<video>::iterator,bool> pObj;

	// is film available?
	filmIter = inventory.find(video(filmName));
	if ( filmIter == inventory.end())
		// film is not in the store's inventory
		cout << "Film " << filmName << " is not in inventory" << endl;
	else if ((*filmIter).getCopies() == 0)
		// all copies are checked out
		cout << "All copies of " << filmName << " are checked out"
			  << endl;
	else
	{
		// decrease the number of copies in the inventory
		// by 1
		(*filmIter).updateCopies(-1);

		// attempt to insert the film into rentalList. if it is
		// inserted, the number of copies will be 1
		pObj = rentals.insert(video(filmName));
		// if film not inserted, increase number of rented copies
		// by 1
		if (pObj.second == false)
			(*(pObj.first)).updateCopies(1);
	}
}

/*
Run:

Initial inventory list:
Frequency (1)
Gladiator (2)
Lord of the Rings (4)
U-571 (2)

Transactions: Enter type (Rent, Return, Done)
followed by film name or space if done

Transaction: Rent Gladiator
Transaction: Rent Frequency
Transaction: Rent Shaft
Film Shaft is not in inventory
Transaction: Rent Frequency
All copies of Frequency are checked out
Transaction: Done

Rented Films:

Frequency (1)
Gladiator (1)

Films Remaining in Inventory:

Frequency (0)
Gladiator (1)
Lord of the Rings (4)
U-571 (2)
*/