package edu.princeton.cs.algs4;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac LinkedBag.java
* Execution: java LinkedBag < input.txt
*
* A generic bag or multiset, implemented using a singly-linked list.
*
* % more tobe.txt
* to be or not to - be - - that - - - is
*
* % java Bag < tobe.txt
* size of bag = 14
* is
* -
* -
* -
* that
* -
* -
* be
* -
* to
* not
* or
* be
* to
*
*************************************************************************/
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* The <tt>LinkedBag</tt> class represents a bag (or multiset) of
* generic items. It supports insertion and iterating over the
* items in arbitrary order.
* <p>
* This implementation uses a singly-linked list with a non-static nested class Node.
* See {@link edu.princeton.cs.algs4.ch13.Bag} for a version that uses a static nested class.
* The <em>add</em>, <em>isEmpty</em>, and <em>size</em> operations
* take constant time. Iteration takes time proportional to the number of items.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/13stacks">Section 1.3</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class LinkedBag<Item> implements Iterable<Item> {
private int N; // number of elements in bag
private Node first; // beginning of bag
// helper linked list class
private class Node {
private Item item;
private Node next;
}
/**
* Initializes an empty bag.
*/
public LinkedBag() {
first = null;
N = 0;
}
/**
* Is this bag empty?
* @return true if this bag is empty; false otherwise
*/
public boolean isEmpty() {
return first == null;
}
/**
* Returns the number of items in this bag.
* @return the number of items in this bag
*/
public int size() {
return N;
}
/**
* Adds the item to this bag.
* @param item the item to add to this bag
*/
public void add(Item item) {
Node oldfirst = first;
first = new Node();
first.item = item;
first.next = oldfirst;
N++;
}
/**
* Returns an iterator that iterates over the items in the bag.
*/
public Iterator<Item> iterator() {
return new ListIterator();
}
// an iterator, doesn't implement remove() since it's optional
private class ListIterator implements Iterator<Item> {
private Node current = first;
public boolean hasNext() { return current != null; }
public void remove() { throw new UnsupportedOperationException(); }
public Item next() {
if (!hasNext()) throw new NoSuchElementException();
Item item = current.item;
current = current.next;
return item;
}
}
/**
* Unit tests the <tt>LinkedBag</tt> data type.
*/
public static void main(String[] args) {
LinkedBag<String> bag = new LinkedBag<String>();
while (!StdIn.isEmpty()) {
String item = StdIn.readString();
bag.add(item);
}
StdOut.println("size of bag = " + bag.size());
for (String s : bag) {
StdOut.println(s);
}
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4-package.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4-package.jar 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 of the License, or
* (at your option) any later version.
*
* algs4-package.jar 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 algs4-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/