/**
* BioJava development code
*
* This code may be freely distributed and modified under the
* terms of the GNU Lesser General Public Licence. This should
* be distributed with the code. If you do not have a copy,
* see:
*
* http://www.gnu.org/copyleft/lesser.html
*
* Copyright for this code is held jointly by the individual
* authors. These should be listed in @author doc comments.
*
* For more information on the BioJava project and its aims,
* or to join the biojava-l mailing list, visit the home page
* at:
*
* http://www.biojava.org/
*
* Created on 5 Mar 2013
* Created by Andreas Prlic
*
* @since 3.0.6
*/
package org.biojava.nbio.structure.math;
import java.io.Serializable;
import java.util.Iterator;
import java.util.SortedMap;
import java.util.TreeMap;
/**
* Sorted symbol table implementation using a java.util.TreeMap.
* Does not allow duplicate keys.
*
* This class represents an ordered symbol table. It assumes that
* the elements are <tt>Comparable</tt>.
* It supports the usual <em>put</em>, <em>get</em>, <em>contains</em>,
* and <em>delete</em> methods.
* It also provides ordered methods for finding the <em>minimum</em>,
* <em>maximum</em>, <em>floor</em>, and <em>ceiling</em>.
* <p>
* The class uses the convention that values cannot be null. Setting the
* value associated with a key to null is equivalent to removing the key.
* <p>
* This implementation uses a balanced binary search tree.
* The <em>add</em>, <em>contains</em>, <em>delete</em>, <em>minimum</em>,
* <em>maximum</em>, <em>ceiling</em>, and <em>floor</em> methods take
* logarithmic time.
*
* Derived from http://introcs.cs.princeton.edu/java/44st/ST.java.html
*
* <p>
* For additional documentation, see <a href="http://introcs.cs.princeton.edu/44st">Section 4.4</a> of
* <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> by Robert Sedgewick and Kevin Wayne.
*
*/
public class SymbolTable<Key extends Comparable<Key>, Value> implements Iterable<Key>, Serializable {
/**
*
*/
private static final long serialVersionUID = -4417561575046471931L;
private TreeMap<Key, Value> st;
/**
* Create an empty symbol table.
*/
public SymbolTable() {
st = new TreeMap<Key, Value>();
}
/**
* Put key-value pair into the symbol table. Remove key from table if
* value is null.
*/
public void put(Key key, Value val) {
if (val == null) st.remove(key);
else st.put(key, val);
}
/**
* Return the value paired with given key; null if key is not in table.
*/
public Value get(Key key) {
return st.get(key);
}
/**
* Delete the key (and paired value) from table.
* Return the value paired with given key; null if key is not in table.
*/
public Value delete(Key key) {
return st.remove(key);
}
/**
* Is the key in the table?
*/
public boolean contains(Key key) {
return st.containsKey(key);
}
/**
* How many keys are in the table?
*/
public int size() {
return st.size();
}
/**
* Return an <tt>Iterator</tt> for the keys in the table.
* To iterate over all of the keys in the symbol table <tt>st</tt>, use the
* foreach notation: <tt>for (Key key : st)</tt>.
*/
@Override
public Iterator<Key> iterator() {
return st.keySet().iterator();
}
/**
* Return an <tt>Iterable</tt> for the keys in the table.
* To iterate over all of the keys in the symbol table <tt>st</tt>, use the
* foreach notation: <tt>for (Key key : st.keys())</tt>.
*/
public Iterable<Key> keys() {
return st.keySet();
}
/**
* Return the smallest key in the table.
*/
public Key min() {
return st.firstKey();
}
/**
* Return the largest key in the table.
*/
public Key max() {
return st.lastKey();
}
/**
* Return the smallest key in the table >= k.
*/
public Key ceil(Key k) {
SortedMap<Key, Value> tail = st.tailMap(k);
if (tail.isEmpty()) return null;
else return tail.firstKey();
}
/**
* Return the largest key in the table <= k.
*/
public Key floor(Key k) {
if (st.containsKey(k)) return k;
// does not include key if present (!)
SortedMap<Key, Value> head = st.headMap(k);
if (head.isEmpty()) return null;
else return head.lastKey();
}
}