package edu.princeton.cs.algs4.ch31;
import edu.princeton.cs.algs4.ch13.Queue;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac SequentialSearchST.java
* Execution: java SequentialSearchST
* Dependencies: StdIn.java StdOut.java
* Data files: http://algs4.cs.princeton.edu/31elementary/tinyST.txt
*
* Symbol table implementation with sequential search in an
* unordered linked list of key-value pairs.
*
* % more tinyST.txt
* S E A R C H E X A M P L E
*
* % java SequentialSearchST < tiny.txt
* L 11
* P 10
* M 9
* X 7
* H 5
* C 4
* R 3
* A 8
* E 12
* S 0
*
*************************************************************************/
/**
* The <tt>SequentialSearchST</tt> class represents an (unordered)
* symbol table of generic key-value pairs.
* It supports the usual <em>put</em>, <em>get</em>, <em>contains</em>,
* <em>delete</em>, <em>size</em>, and <em>is-empty</em> methods.
* It also provides a <em>keys</em> method for iterating over all of the keys.
* A symbol table implements the <em>associative array</em> abstraction:
* when associating a value with a key that is already in the symbol table,
* the convention is to replace the old value with the new value.
* The class also uses the convention that values cannot be <tt>null</tt>. Setting the
* value associated with a key to <tt>null</tt> is equivalent to deleting the key
* from the symbol table.
* <p>
* This implementation uses a singly-linked list and sequential search.
* It relies on the <tt>equals()</tt> method to test whether two keys
* are equal. It does not call either the <tt>compareTo()</tt> or
* <tt>hashCode()</tt> method.
* The <em>put</em> and <em>delete</em> operations take linear time; the
* <em>get</em> and <em>contains</em> operations takes linear time in the worst case.
* The <em>size</em>, and <em>is-empty</em> operations take constant time.
* Construction takes constant time.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/31elementary">Section 3.1</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class SequentialSearchST<Key, Value> {
private int N; // number of key-value pairs
private Node first; // the linked list of key-value pairs
// a helper linked list data type
private class Node {
private Key key;
private Value val;
private Node next;
public Node(Key key, Value val, Node next) {
this.key = key;
this.val = val;
this.next = next;
}
}
/**
* Initializes an empty symbol table.
*/
public SequentialSearchST() {
}
/**
* Returns the number of key-value pairs in this symbol table.
* @return the number of key-value pairs in this symbol table
*/
public int size() {
return N;
}
/**
* Is this symbol table empty?
* @return <tt>true</tt> if this symbol table is empty and <tt>false</tt> otherwise
*/
public boolean isEmpty() {
return size() == 0;
}
/**
* Does this symbol table contain the given key?
* @param key the key
* @return <tt>true</tt> if this symbol table contains <tt>key</tt> and
* <tt>false</tt> otherwise
*/
public boolean contains(Key key) {
return get(key) != null;
}
/**
* Returns the value associated with the given key.
* @param key the key
* @return the value associated with the given key if the key is in the symbol table
* and <tt>null</tt> if the key is not in the symbol table
*/
public Value get(Key key) {
for (Node x = first; x != null; x = x.next) {
if (key.equals(x.key)) return x.val;
}
return null;
}
/**
* Inserts the key-value pair into the symbol table, overwriting the old value
* with the new value if the key is already in the symbol table.
* If the value is <tt>null</tt>, this effectively deletes the key from the symbol table.
* @param key the key
* @param val the value
*/
public void put(Key key, Value val) {
if (val == null) { delete(key); return; }
for (Node x = first; x != null; x = x.next)
if (key.equals(x.key)) { x.val = val; return; }
first = new Node(key, val, first);
N++;
}
/**
* Removes the key and associated value from the symbol table
* (if the key is in the symbol table).
* @param key the key
*/
public void delete(Key key) {
first = delete(first, key);
}
// delete key in linked list beginning at Node x
// warning: function call stack too large if table is large
private Node delete(Node x, Key key) {
if (x == null) return null;
if (key.equals(x.key)) { N--; return x.next; }
x.next = delete(x.next, key);
return x;
}
/**
* Returns all keys in the symbol table as an <tt>Iterable</tt>.
* To iterate over all of the keys in the symbol table named <tt>st</tt>,
* use the foreach notation: <tt>for (Key key : st.keys())</tt>.
* @return all keys in the sybol table as an <tt>Iterable</tt>
*/
public Iterable<Key> keys() {
Queue<Key> queue = new Queue<Key>();
for (Node x = first; x != null; x = x.next)
queue.enqueue(x.key);
return queue;
}
/**
* Unit tests the <tt>SequentialSearchST</tt> data type.
*/
public static void main(String[] args) {
SequentialSearchST<String, Integer> st = new SequentialSearchST<String, Integer>();
for (int i = 0; !StdIn.isEmpty(); i++) {
String key = StdIn.readString();
st.put(key, i);
}
for (String s : st.keys())
StdOut.println(s + " " + st.get(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.
*************************************************************************/