package edu.princeton.cs.algs4.ch31;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac ST.java
* Execution: java ST
*
* Sorted symbol table implementation using a java.util.TreeMap.
* Does not allow duplicates.
*
* % java ST
*
*************************************************************************/
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.TreeMap;
/**
* The <tt>ST</tt> class represents an ordered 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 ordered methods for finding the <em>minimum</em>,
* <em>maximum</em>, <em>floor</em>, and <em>ceiling</em>.
* 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.
* Unlike {@link java.util.Map}, this class 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 balanced binary search tree. It requires that
* the key type implements the <tt>Comparable</tt> interface and calls the
* <tt>compareTo()</tt> and method to compare two keys. It does not call either
* <tt>equals()</tt> or <tt>hashCode()</tt>.
* The <em>put</em>, <em>contains</em>, <em>remove</em>, <em>minimum</em>,
* <em>maximum</em>, <em>ceiling</em>, and <em>floor</em> operations each take
* logarithmic 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/35applications">Section 3.5</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*/
public class ST<Key extends Comparable<Key>, Value> implements Iterable<Key> {
private TreeMap<Key, Value> st;
/**
* Initializes an empty symbol table.
*/
public ST() {
st = new TreeMap<Key, Value>();
}
/**
* 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
* @throws NullPointerException if <tt>key</tt> is <tt>null</tt>
*/
public Value get(Key key) {
if (key == null) throw new NullPointerException("called get() with null key");
return st.get(key);
}
/**
* 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
* @throws NullPointerException if <tt>key</tt> is <tt>null</tt>
*/
public void put(Key key, Value val) {
if (key == null) throw new NullPointerException("called put() with null key");
if (val == null) st.remove(key);
else st.put(key, val);
}
/**
* Removes the key and associated value from the symbol table
* (if the key is in the symbol table).
* @param key the key
* @throws NullPointerException if <tt>key</tt> is <tt>null</tt>
*/
public void delete(Key key) {
if (key == null) throw new NullPointerException("called delete() with null key");
st.remove(key);
}
/**
* 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
* @throws NullPointerException if <tt>key</tt> is <tt>null</tt>
*/
public boolean contains(Key key) {
if (key == null) throw new NullPointerException("called contains() with null key");
return st.containsKey(key);
}
/**
* 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 st.size();
}
/**
* 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;
}
/**
* 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() {
return st.keySet();
}
/**
* Returns all of the keys in the symbol table as an iterator.
* To iterate over all of the keys in a symbol table named <tt>st</tt>, use the
* foreach notation: <tt>for (Key key : st)</tt>.
* @deprecated Use {@link #keys} instead.
* This method is provided for backward compatibility with the version from
* <em>Introduction to Programming in Java: An Interdisciplinary Approach.</em>
* @return an iterator to all of the keys in the symbol table
*/
public Iterator<Key> iterator() {
return st.keySet().iterator();
}
/**
* Returns the smallest key in the symbol table.
* @return the smallest key in the symbol table
* @throws NoSuchElementException if the symbol table is empty
*/
public Key min() {
if (isEmpty()) throw new NoSuchElementException("called min() with empty symbol table");
return st.firstKey();
}
/**
* Returns the largest key in the symbol table.
* @return the largest key in the symbol table
* @throws NoSuchElementException if the symbol table is empty
*/
public Key max() {
if (isEmpty()) throw new NoSuchElementException("called max() with empty symbol table");
return st.lastKey();
}
/**
* Returns the smallest key in the symbol table greater than or equal to <tt>key</tt>.
* @return the smallest key in the symbol table greater than or equal to <tt>key</tt>
* @param key the key
* @throws NoSuchElementException if there is no such key
* @throws NullPointerException if <tt>key</tt> is <tt>null</tt>
*/
public Key ceiling(Key key) {
if (key == null) throw new NullPointerException("called ceiling() with null key");
Key k = st.ceilingKey(key);
if (k == null) throw new NoSuchElementException("all keys are less than " + key);
return k;
}
/**
* Returns the largest key in the symbol table less than or equal to <tt>key</tt>.
* @return the largest key in the symbol table less than or equal to <tt>key</tt>
* @param key the key
* @throws NoSuchElementException if there is no such key
* @throws NullPointerException if <tt>key</tt> is <tt>null</tt>
*/
public Key floor(Key key) {
if (key == null) throw new NullPointerException("called floor() with null key");
Key k = st.floorKey(key);
if (k == null) throw new NoSuchElementException("all keys are greater than " + key);
return k;
}
/**
* Unit tests the <tt>ST</tt> data type.
*/
public static void main(String[] args) {
ST<String, Integer> st = new ST<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.
*************************************************************************/