Class BinarySearchST<Key extends Comparable<Key>,​Value>


  • public class BinarySearchST<Key extends Comparable<Key>,​Value>
    extends Object
    The BST 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, select, 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 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.

    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().

    This implementation uses a sorted array. The put and remove operations take Θ(n) time in the worst case. The contains, ceiling, floor, and rank operations take Θ(log n) time in the worst case. The size, is-empty, minimum, maximum, and select operations take Θ(1) time. Construction takes Θ(1) time.

    For alternative implementations of the symbol table API, see ST, BST, SequentialSearchST, RedBlackBST, SeparateChainingHashST, and LinearProbingHashST, For additional documentation, see Section 3.1 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

    • Constructor Summary

      Constructors 
      Constructor Description
      BinarySearchST()
      Initializes an empty symbol table.
      BinarySearchST​(int capacity)
      Initializes an empty symbol table with the specified initial capacity.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      Key ceiling​(Key key)
      Returns the smallest key in this symbol table greater than or equal to key.
      boolean contains​(Key key)
      Does this symbol table contain the given key?
      void delete​(Key key)
      Removes the specified key and associated value from this symbol table (if the key is in the symbol table).
      void deleteMax()
      Removes the largest key and associated value from this symbol table.
      void deleteMin()
      Removes the smallest key and associated value from this symbol table.
      Key floor​(Key key)
      Returns the largest key in this symbol table less than or equal to key.
      Value get​(Key key)
      Returns the value associated with the given key in this symbol table.
      boolean isEmpty()
      Returns true if this symbol table is empty.
      Iterable<Key> keys()
      Returns all keys in this symbol table as an Iterable.
      Iterable<Key> keys​(Key lo, Key hi)
      Returns all keys in this symbol table in the given range, as an Iterable.
      static void main​(String[] args)
      Unit tests the BinarySearchST data type.
      Key max()
      Returns the largest key in this symbol table.
      Key min()
      Returns the smallest key in this symbol table.
      void put​(Key key, Value val)
      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.
      int rank​(Key key)
      Returns the number of keys in this symbol table strictly less than key.
      Key select​(int k)
      Return the kth smallest key in this symbol table.
      int size()
      Returns the number of key-value pairs in this symbol table.
      int size​(Key lo, Key hi)
      Returns the number of keys in this symbol table in the specified range.
    • Constructor Detail

      • BinarySearchST

        public BinarySearchST()
        Initializes an empty symbol table.
      • BinarySearchST

        public BinarySearchST​(int capacity)
        Initializes an empty symbol table with the specified initial capacity.
        Parameters:
        capacity - the maximum capacity
    • Method Detail

      • size

        public int size()
        Returns the number of key-value pairs in this symbol table.
        Returns:
        the number of key-value pairs in this symbol table
      • isEmpty

        public boolean isEmpty()
        Returns true if this symbol table is empty.
        Returns:
        true if this symbol table is empty; false otherwise
      • contains

        public boolean contains​(Key key)
        Does this symbol table contain the given key?
        Parameters:
        key - the key
        Returns:
        true if this symbol table contains key and false otherwise
        Throws:
        IllegalArgumentException - if key is null
      • get

        public Value get​(Key key)
        Returns the value associated with the given key in this symbol table.
        Parameters:
        key - the key
        Returns:
        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:
        IllegalArgumentException - if key is null
      • rank

        public int rank​(Key key)
        Returns the number of keys in this symbol table strictly less than key.
        Parameters:
        key - the key
        Returns:
        the number of keys in the symbol table strictly less than key
        Throws:
        IllegalArgumentException - if key is null
      • put

        public void put​(Key key,
                        Value val)
        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. Deletes the specified key (and its associated value) from this symbol table if the specified value is null.
        Parameters:
        key - the key
        val - the value
        Throws:
        IllegalArgumentException - if key is null
      • delete

        public void delete​(Key key)
        Removes the specified key and associated value from this symbol table (if the key is in the symbol table).
        Parameters:
        key - the key
        Throws:
        IllegalArgumentException - if key is null
      • deleteMin

        public void deleteMin()
        Removes the smallest key and associated value from this symbol table.
        Throws:
        NoSuchElementException - if the symbol table is empty
      • deleteMax

        public void deleteMax()
        Removes the largest key and associated value from this symbol table.
        Throws:
        NoSuchElementException - if the symbol table is empty
      • min

        public Key min()
        Returns the smallest key in this symbol table.
        Returns:
        the smallest key in this symbol table
        Throws:
        NoSuchElementException - if this symbol table is empty
      • max

        public Key max()
        Returns the largest key in this symbol table.
        Returns:
        the largest key in this symbol table
        Throws:
        NoSuchElementException - if this symbol table is empty
      • select

        public Key select​(int k)
        Return the kth smallest key in this symbol table.
        Parameters:
        k - the order statistic
        Returns:
        the kth smallest key in this symbol table
        Throws:
        IllegalArgumentException - unless k is between 0 and n–1
      • floor

        public Key floor​(Key key)
        Returns the largest key in this symbol table less than or equal to key.
        Parameters:
        key - the key
        Returns:
        the largest key in this symbol table less than or equal to key
        Throws:
        NoSuchElementException - if there is no such key
        IllegalArgumentException - if key is null
      • ceiling

        public Key ceiling​(Key key)
        Returns the smallest key in this symbol table greater than or equal to key.
        Parameters:
        key - the key
        Returns:
        the smallest key in this symbol table greater than or equal to key
        Throws:
        NoSuchElementException - if there is no such key
        IllegalArgumentException - if key is null
      • size

        public int size​(Key lo,
                        Key hi)
        Returns the number of keys in this symbol table in the specified range.
        Parameters:
        lo - minimum endpoint
        hi - maximum endpoint
        Returns:
        the number of keys in this symbol table between lo (inclusive) and hi (inclusive)
        Throws:
        IllegalArgumentException - if either lo or hi is null
      • keys

        public Iterable<Key> keys()
        Returns all keys in this 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()).
        Returns:
        all keys in this symbol table
      • keys

        public Iterable<Key> keys​(Key lo,
                                  Key hi)
        Returns all keys in this symbol table in the given range, as an Iterable.
        Parameters:
        lo - minimum endpoint
        hi - maximum endpoint
        Returns:
        all keys in this symbol table between lo (inclusive) and hi (inclusive)
        Throws:
        IllegalArgumentException - if either lo or hi is null
      • main

        public static void main​(String[] args)
        Unit tests the BinarySearchST data type.
        Parameters:
        args - the command-line arguments