/*************************************************************************
* 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.SortedMap;
import java.util.TreeMap;
/**
* This class represents an ordered symbol table. It assumes that
* the elements are Comparable.
* It supports the usual put, get, contains,
* and remove methods.
* It also provides ordered methods for finding the minimum,
* maximum, floor, and ceiling.
*
* 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.
*
* This class implements the Iterable interface for compatiblity with
* the version from Introduction to Programming in Java: An Interdisciplinary
* Approach.
*
* This implementation uses a balanced binary search tree.
* The add, contains, remove, minimum,
* maximum, ceiling, and floor methods take
* logarithmic time.
*
* For additional documentation, see Section 4.5 of
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
*/
public class ST, Value> implements Iterable {
private TreeMap st;
/**
* Create an empty symbol table.
*/
public ST() {
st = new TreeMap();
}
/**
* 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 Iterable for the keys in the table.
* To iterate over all of the keys in the symbol table st, use the
* foreach notation: for (Key key : st.keys()).
*/
public Iterable keys() {
return st.keySet();
}
/**
* Return an Iterator for the keys in the table.
* To iterate over all of the keys in the symbol table st, use the
* foreach notation: for (Key key : st).
* This method is for backward compatibility with the version from Introduction
* to Programming in Java: An Interdisciplinary Approach.
*/
public Iterator iterator() {
return st.keySet().iterator();
}
/**
* 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 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 head = st.headMap(k);
if (head.isEmpty()) return null;
else return head.lastKey();
}
/***********************************************************************
* Test routine.
**********************************************************************/
public static void main(String[] args) {
ST st = new ST();
// insert some key-value pairs
st.put("www.cs.princeton.edu", "128.112.136.11");
st.put("www.cs.princeton.edu", "128.112.136.35"); // overwrite old value
st.put("www.princeton.edu", "128.112.130.211");
st.put("www.math.princeton.edu", "128.112.18.11");
st.put("www.yale.edu", "130.132.51.8");
st.put("www.amazon.com", "207.171.163.90");
st.put("www.simpsons.com", "209.123.16.34");
st.put("www.stanford.edu", "171.67.16.120");
st.put("www.google.com", "64.233.161.99");
st.put("www.ibm.com", "129.42.16.99");
st.put("www.apple.com", "17.254.0.91");
st.put("www.slashdot.com", "66.35.250.150");
st.put("www.whitehouse.gov", "204.153.49.136");
st.put("www.espn.com", "199.181.132.250");
st.put("www.snopes.com", "66.165.133.65");
st.put("www.movies.com", "199.181.132.250");
st.put("www.cnn.com", "64.236.16.20");
st.put("www.iitb.ac.in", "202.68.145.210");
StdOut.println(st.get("www.cs.princeton.edu"));
StdOut.println(st.get("www.harvardsucks.com"));
StdOut.println(st.get("www.simpsons.com"));
StdOut.println();
StdOut.println("ceil(www.simpsonr.com) = " + st.ceil("www.simpsonr.com"));
StdOut.println("ceil(www.simpsons.com) = " + st.ceil("www.simpsons.com"));
StdOut.println("ceil(www.simpsont.com) = " + st.ceil("www.simpsont.com"));
StdOut.println("floor(www.simpsonr.com) = " + st.floor("www.simpsonr.com"));
StdOut.println("floor(www.simpsons.com) = " + st.floor("www.simpsons.com"));
StdOut.println("floor(www.simpsont.com) = " + st.floor("www.simpsont.com"));
StdOut.println();
StdOut.println("min key: " + st.min());
StdOut.println("max key: " + st.max());
StdOut.println("size: " + st.size());
StdOut.println();
// print out all key-value pairs in lexicographic order
for (String s : st.keys())
StdOut.println(s + " " + st.get(s));
}
}