ave more data)         private int iData; // data item (key)         //--------------------------------------------------------------         public DataItem(int ii) // constructor         { iData = ii; }         //--------------------------------------------------------------         public int getKey()         { return iData; }

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Question

Modify the hash.java program to use quadratic probing instead of linear probing.

 

// hash.java
// demonstrates hash table with linear probing
import java.io.*;
    ////////////////////////////////////////////////////////////////
    class DataItem
    { // (could have more data)
        private int iData; // data item (key)
        //--------------------------------------------------------------
        public DataItem(int ii) // constructor
        { iData = ii; }
        //--------------------------------------------------------------
        public int getKey()
        { return iData; }
//--------------------------------------------------------------
    } // end class DataItem
    ////////////////////////////////////////////////////////////////
    class HashTable
    {
        private DataItem[] hashArray; // array holds hash table
        private int arraySize;

        private DataItem nonItem; // for deleted items
        // -------------------------------------------------------------
        public HashTable(int size) // constructor
        {
            arraySize = size;
            hashArray = new DataItem[arraySize];
            nonItem = new DataItem(-1); // deleted item key is -1
        }
        // -------------------------------------------------------------
        public void displayTable()
        {
            System.out.print("Table: ");
            for(int j=0; j<arraySize; j++)
            {
                if(hashArray[j] != null)
                    System.out.print(hashArray[j].getKey() +" ");

                else
                    System.out.print("**  ");

            }
            System.out.println("");
        }
        // -------------------------------------------------------------
        public int hashFunc(int key)
        {
            return key % arraySize; // hash function
        }
        // -------------------------------------------------------------
        public void insert(DataItem item) // insert a DataItem
// (assumes table not full)
        {
            int key = item.getKey(); // extract key
            int hashVal = hashFunc(key); // hash the key
// until empty cell or -1,
            while(hashArray[hashVal] != null &&
                    hashArray[hashVal].getKey() != -1)
            {
                ++hashVal; // go to next cell
                hashVal %= arraySize; // wraparound if necessary
            }
            hashArray[hashVal] = item; // insert item
        } // end insert()
        // -------------------------------------------------------------
        public DataItem delete(int key) // delete a DataItem
        {
            int hashVal = hashFunc(key); // hash the key
            while(hashArray[hashVal] != null) // until empty cell,
            { // found the key?
                if(hashArray[hashVal].getKey() == key)
                {
                    DataItem temp = hashArray[hashVal]; // save item
                    hashArray[hashVal] = nonItem; // delete item
                    return temp; // return item
                }
                ++hashVal; // go to next cell
                hashVal %= arraySize; // wraparound if necessary
            }
            return null; // can’t find item
        } // end delete()
        // -------------------------------------------------------------
        public DataItem find(int key) // find item with key
        {
            int hashVal = hashFunc(key); // hash the key
            while(hashArray[hashVal] != null) // until empty cell,
            { // found the key?
                if(hashArray[hashVal].getKey() == key)
                    return hashArray[hashVal]; // yes, return item
                ++hashVal; // go to next cell
                hashVal %= arraySize; // wraparound if necessary
            }
            return null; // can’t find item
        }
// -------------------------------------------------------------
    } // end class HashTable
    ////////////////////////////////////////////////////////////////

 

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