/******************************************************************************
* Compilation: javac ST.java
* Execution: java ST
* Dependencies: StdIn.java StdOut.java
*
* 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 {@code ST} 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>remove</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 {@code null}—setting the
* value associated with a key to {@code null} 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 {@code Comparable} interface and calls the
* {@code compareTo()} and method to compare two keys. It does not call either
* {@code equals()} or {@code hashCode()}.
* 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://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.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*
* @param <Key> the generic type of keys in this symbol table
* @param <Value> the generic type of values in this symbol table
*/
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 in this symbol table.
*
* @param key the key
* @return the value associated with the given key if the key is in this symbol table;
* {@code null} if the key is not in this symbol table
* @throws IllegalArgumentException if {@code key} is {@code null}
*/
public Value get(Key key) {
if (key == null) throw new IllegalArgumentException("called get() with null key");
return st.get(key);
}
/**
* Inserts the specified key-value pair into the symbol table, overwriting the old
* value with the new value if the symbol table already contains the specified key.
* Removes the specified key (and its associated value) from this symbol table
* if the specified value is {@code null}.
*
* @param key the key
* @param val the value
* @throws IllegalArgumentException if {@code key} is {@code null}
*/
public void put(Key key, Value val) {
if (key == null) throw new IllegalArgumentException("called put() with null key");
if (val == null) st.remove(key);
else st.put(key, val);
}
/**
* Removes the specified key and its associated value from this symbol table
* (if the key is in this symbol table).
*
* @param key the key
* @throws IllegalArgumentException if {@code key} is {@code null}
* @deprecated Replaced by {@link #remove(Comparable key)}.
*/
@Deprecated
public void delete(Key key) {
if (key == null) throw new IllegalArgumentException("called delete() with null key");
st.remove(key);
}
/**
* Removes the specified key and its associated value from this symbol table
* (if the key is in this symbol table).
*
* @param key the key
* @throws IllegalArgumentException if {@code key} is {@code null}
*/
public void remove(Key key) {
if (key == null) throw new IllegalArgumentException("called remove() with null key");
st.remove(key);
}
/**
* Returns true if this symbol table contain the given key.
*
* @param key the key
* @return {@code true} if this symbol table contains {@code key} and
* {@code false} otherwise
* @throws IllegalArgumentException if {@code key} is {@code null}
*/
public boolean contains(Key key) {
if (key == null) throw new IllegalArgumentException("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();
}
/**
* Returns true if this symbol table is empty.
*
* @return {@code true} if this symbol table is empty and {@code false} otherwise
*/
public boolean isEmpty() {
return size() == 0;
}
/**
* Returns all keys in this symbol table.
* <p>
* To iterate over all of the keys in the symbol table named {@code st},
* use the foreach notation: {@code for (Key key : st.keys())}.
*
* @return all keys in this symbol table
*/
public Iterable<Key> keys() {
return st.keySet();
}
/**
* Returns all of the keys in this symbol table.
* To iterate over all of the keys in a symbol table named {@code st}, use the
* foreach notation: {@code for (Key key : st)}.
*
* @return an iterator to all of the keys in this symbol table
* @deprecated Replaced by {@link #keys()}.
*/
@Deprecated
public Iterator<Key> iterator() {
return st.keySet().iterator();
}
/**
* Returns the smallest key in this symbol table.
*
* @return the smallest key in this symbol table
* @throws NoSuchElementException if this 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 this symbol table.
*
* @return the largest key in this symbol table
* @throws NoSuchElementException if this 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 this symbol table greater than or equal to {@code key}.
*
* @param key the key
* @return the smallest key in this symbol table greater than or equal to {@code key}
* @throws NoSuchElementException if there is no such key
* @throws IllegalArgumentException if {@code key} is {@code null}
*/
public Key ceiling(Key key) {
if (key == null) throw new IllegalArgumentException("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 this symbol table less than or equal to {@code key}.
*
* @param key the key
* @return the largest key in this symbol table less than or equal to {@code key}
* @throws NoSuchElementException if there is no such key
* @throws IllegalArgumentException if {@code key} is {@code null}
*/
public Key floor(Key key) {
if (key == null) throw new IllegalArgumentException("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 {@code ST} 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));
}
}