package stdlibpack;
/*************************************************************************
* 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.SortedMap;
import java.util.TreeMap;
/**
* The ST class represents an ordered symbol table of generic
* key-value pairs.
* It supports the usual put, get, contains,
* delete, size, and is-empty methods.
* It also provides ordered methods for finding the minimum,
* maximum, floor, and ceiling.
* It also provides a keys method for iterating over all of the keys.
* A symbol table implements the associative array 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 null—setting the
* value associated with a key to null is equivalent to deleting the key
* from the symbol table.
*
* This implementation uses a balanced binary search tree. It requires that
* the key type implements the Comparable interface and calls the
* compareTo() and method to compare two keys. It does not call either
* equals() or hashCode().
* The put, contains, remove, minimum,
* maximum, ceiling, and floor operations each take
* logarithmic time in the worst case.
* The size, and is-empty operations take constant time.
* Construction takes constant time.
*
* For additional documentation, see Section 4.4 of
* Introduction to Programming in Java: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne.
*/
public class ST, Value> implements Iterable {
private TreeMap st;
/**
* Initializes an empty symbol table.
*/
public ST() {
st = new TreeMap();
}
/**
* 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 null if the key is not in the symbol table
* @throws NullPointerException if key is null
*/
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 null, this effectively deletes the key from the symbol table.
* @param key the key
* @param val the value
* @throws NullPointerException if key is null
*/
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 key is null
*/
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 true if this symbol table contains key and
* false otherwise
* @throws NullPointerException if key is null
*/
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 true if this symbol table is empty and false otherwise
*/
public boolean isEmpty() {
return size() == 0;
}
/**
* Returns all keys in the symbol table as an Iterable.
* To iterate over all of the keys in the symbol table named st,
* use the foreach notation: for (Key key : st.keys()).
* @return all keys in the sybol table as an Iterable
*/
public Iterable 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 st, use the
* foreach notation: for (Key key : st).
* @return an iterator to all of the keys in the symbol table
*/
public Iterator 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 key.
* @return the smallest key in the symbol table greater than or equal to key
* @param key the key
* @throws NoSuchElementException if the symbol table is empty
* @throws NullPointerException if key is null
*/
public Key ceil(Key key) {
if (key == null) throw new NullPointerException("called ceil() with null key");
SortedMap tail = st.tailMap(key);
if (tail.isEmpty()) throw new NoSuchElementException();
return tail.firstKey();
}
/**
* Returns the largest key in the symbol table less than or equal to key.
* @return the largest key in the symbol table less than or equal to key
* @param key the key
* @throws NoSuchElementException if the symbol table is empty
* @throws NullPointerException if key is null
*/
public Key floor(Key key) {
if (key == null) throw new NullPointerException("called floor() with null key");
// headMap does not include key if present (!)
if (st.containsKey(key)) return key;
SortedMap head = st.headMap(key);
if (head.isEmpty()) throw new NoSuchElementException();
return head.lastKey();
}
/**
* Unit tests the ST data type.
*/
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));
}
}