Question

IN JAVA LANGUAGE:

For this lab you are required for implement the following methods:

1. public QuadraticProbingHashTable( int size ):

As the signature of this method suggests, this is a constructor for this class. This constructor will initialize status of an object from this class based on the input parameter (i.e., size). So, this function will create the array HashTable with the specified size and initialize all of its elements to be null.

2. public int hash(int value, int tableSize ):

This method accepts an integer value and returns the hash value based on the table size. Note that you are supposed to use mod operator as we saw in class for your hash function. That means the hash value you are returning is going to be a number between 0 and tableSize-1. The input value can be positive or negative. This function is not supposed to handle the probing. Collision handling and probing should be part of your insert function (or another helper function).

3. public void insert( int x )

This function accepts a value (called x) and insert it into the hash table. If the item is already in the table, this method does nothing and returns. You need to resolve collision using quadratic probing. It is highly recommended that you write a helper function to do this (but this is not mandatory). Note that other fields of this class has to be updated accordingly after the insert. If the load factor of the table is 0.75 or higher after the insert, this function should perform rehashing as instructed below. For this assignment, check the load factor first (assuming that the value will be added to the table), if rehash is required, rehash first and then insert the value.

4. public void rehash( )

This function will increase the size of the hash table by a factor of two and rehash the elements into the new hash table (your insert method should call the rehash function as soon as the load factor of the hash table is equal or greater than 0.75.

do NOT change any signature (parameters) in any method.

no need to actually run the program. other files are required but not for this portion just yet.

package lab10; public class QuadraticProbingHashTable public HashEntry HashTable; I/ The array that holds the hash table public int currentSize; // The number of occupied cells // constructor to create the HashTable of initiaľ size = size // and sets all of its elements to null public QuadraticProbingHashTable ( int size ) // FILL IN // insert into the hash table // if the item is already present, do nothing and simply return // be careful you might need to rehash - reshape when the load factor is .75 // Hint: first check the load factor after add if the size is beyond rehash first! public void insert( int x) //FILL IN // this function will increase the size of the hash table by a factor of two /7 and do the rehash of the current elements inside the hash table public void rehash) // FILL IN // a simple hash function for int values /1 the hash value should be a number between and tablesize-1 // use the mod operator as suggested in class public int hash(int value, int tableSize) // FILL IN DO NOT RETURN-1 return -1

Answer 1

PROGRAM

public class QuadraticProbingHashTable

{

public HashEntry[] HashTable;

public int currentSize;

double load;

int size;

public QuadraticProbingHashTable(int size)

{

currentSize=0;

load=0;

this.size=size;

HashTable=new HashTable[size];

for(int i=0;i<size;i++)

HashTable[i]=null;

}

public void insert(int x)

{

if(load>=0.75)

rehash();

else

{

if(!search(x))

{

int h=hash(x,size);

HashTable[h]=x;

currentSize++;

load=(double)currentSize/(double)size;

if(load>=0.75)

rehash();

}

}

}

public boolean search(int x)

{

for(int i=0;i<size;i++)

{

if(x==HashTable[i])

{

return true;

}

}

return false;

}

public int hash(int value,int tablesize)

{

int h=value%tablesize;

if(HashTable[h]==null)

return h;

else

h=quadratic(value,tablesize);

return h;

}

public void rehash()

{

HashTable[] ht=new HashTable[size];

ht=HashTable;

HashTable=new HashTable[size*2];

size=size*2;

for(int i=0;i<size/2;i++)

{

if(ht[i]!=null)

{

insert(ht[i],size);

}

}

}

public int quadratic(int x,int tablesize)

{

int h,i=1;

h=x%tablesize;

while(true)

{

if(HashTable[h+i*i]==null)

return h+i*i;

else

i++;

}

}

}

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