Ninth Commit

Author: Chavez0296

Hashtable/HashDoubleApp.java

@@ -0,0 +1,176 @@
+package Hashtable;
+import java.io.*;
+
+class DataItem
+{
+    private int iData;
+//----------------------------------------------------------------------------------//
+    public DataItem(int ii)
+    {
+        iData = ii;
+    }
+//----------------------------------------------------------------------------------// 
+    public int getKey()
+    {
+        return iData;
+    }
+}
+//----------------------------------------------------------------------------------//
+class HashTable
+{
+    private DataItem[] hashArray;
+    private int arraySize;
+    private DataItem nonitem;
+//----------------------------------------------------------------------------------//
+    public HashTable(int size)
+    {
+        arraySize = size;
+        hashArray = new DataItem[arraySize];
+        nonitem = new DataItem(-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 hashFunc1(int key)
+    {
+        return key % arraySize;
+    }
+//----------------------------------------------------------------------------------//
+    public int hashFunc2(int key)
+    {
+        return 5 - key % 5; //non-zero, less than array size, different from hF1 (array size must be relatively prime to 5, 4, 3, and 2)
+    }
+//----------------------------------------------------------------------------------//
+    public void insert(int key, DataItem item) //assumes table is not full
+    {   
+        int hashVal = hashFunc1(key); // hash the key
+        int stepSize = hashFunc2(key);// get step siz until empty cell or -1
+
+        while(hashArray[hashVal] != null && hashArray[hashVal].getKey() != -1)
+        {
+            hashVal += stepSize; //add the step
+            hashVal %= arraySize;//for the wrap around
+        }
+        hashArray[hashVal] = item; //insert item
+    }
+//----------------------------------------------------------------------------------//
+    public DataItem delete(int key)
+    {
+        int hashVal = hashFunc1(key);
+        int stepSize = hashFunc2(key);
+
+        while(hashArray[hashVal] != null)//until empty cell, is correct hashVal?
+        {
+            if(hashArray[hashVal].getKey() == key)
+            {
+                DataItem temp = hashArray[hashVal]; //save item
+                hashArray[hashVal] = nonitem; // delete item
+                return temp;                   //return item
+            }
+            hashVal += stepSize;
+            hashVal %= arraySize;
+        }
+        return null;
+    }
+//----------------------------------------------------------------------------------//
+    public DataItem find(int key) //assumes table is not full **find item key**
+    {
+        int hashVal = hashFunc1(key);
+        int stepSize = hashFunc2(key);
+
+        while(hashArray[hashVal] != null)
+        {
+            if(hashArray[hashVal].getKey() == key) // found?
+                return hashArray[hashVal];         // return item
+            hashVal += stepSize;                   //add the step
+            hashVal %= arraySize;                  //for wraparound
+        }
+        return null;
+    }
+//----------------------------------------------------------------------------------//
+}
+class HashDoubleApp {
+    public static void main(String[] args) throws IOException
+    {   
+        int aKey;
+        DataItem aDataItem;
+        int size, n;
+
+        System.out.print("Enter size of hash table: ");
+        size = getInt();
+        System.out.print("Enter initial number of items: ");
+        n = getInt();
+
+        HashTable theHashTable = new HashTable(size); //make table
+
+        for(int i = 0; i < n; i++) //insert data
+        {
+            aKey = (int)(java.lang.Math.random() * 2 * size); // between 
+            aDataItem = new DataItem(aKey);
+            theHashTable.insert(aKey, aDataItem);    
+        }
+
+        while(true)
+        {
+            System.out.print("Enter first letter of ");
+            System.out.print("show, insert, delete, or find: ");
+            char choice = getChar();
+
+            switch (choice) {
+                case 's':
+                    theHashTable.displayTable();
+                    break;
+                case 'i':
+                    System.out.print("Enter key value to insert: ");
+                    aKey = getInt();
+                    aDataItem = new DataItem(aKey);
+                    theHashTable.insert(aKey, aDataItem);
+                    break;
+                case 'd':
+                    System.out.print("Enter key value to delete: ");
+                    aKey = getInt();
+                    theHashTable.delete(aKey);
+                    break;
+                case 'f':
+                    System.out.print("Enter key value to find: ");
+                    aKey = getInt();
+                    aDataItem = theHashTable.find(aKey);
+                    if(aDataItem != null)
+                        System.out.println("Found " + aKey);
+                    else
+                        System.out.println("Could not find " + aKey);
+                    break;
+                default:
+                    System.out.println("Invalid entry.\n");
+            }
+        }
+    }
+    public static String getString() throws IOException
+    {
+        InputStreamReader isr = new InputStreamReader(System.in);
+        BufferedReader br = new BufferedReader(isr);
+        String s = br.readLine();
+        return s;
+    }
+    public static char getChar() throws IOException
+    {
+        String s = getString();
+        return s.charAt(0);
+    }   
+    public static int getInt() throws IOException
+    {
+        String s = getString();
+        return Integer.parseInt(s);
+    }
+}