public class QuadraticProbingHashTable<T> {
private static final int DEFAULT_TABLE_SIZE=10;
private HashEntry<T>[] array;
private int currentsize;
public QuadraticProbingHashTable(){
this(DEFAULT_TABLE_SIZE);
}
public QuadraticProbingHashTable(int size){
allocateArray(size);
makeEmpty();
}
public void makeEmpty(){
currentsize=0;
for(int i=0;i<array.length;i++){
array[i]=null;
}
}
public boolean contain(T val){
int address=findPos(val);
return isActive(address);
}
public void remove(T val){
int address=findPos(val);
if(isActive(address)){
array[address].active=false;
}
currentsize--;
}
public void insert(T val){
int address=findPos(val);
if((isActive(address)))
return;
array[address]=new HashEntry<T>(val, true);
if(++currentsize>array.length/2){
rehash();
}
}
private static class HashEntry<T>{
public T val;
public boolean active;
public HashEntry(T val){
this(val,true);
}
public HashEntry(T val,boolean active){
this.val=val;
this.active=active;
}
}
private void allocateArray(int arraySize){
array=new HashEntry[nextPrime(arraySize)];
}
private boolean isActive(int currentPos){
return array[currentPos]!=null&&array[currentPos].active;
}
private int findPos(T val){
int num=1;
int currentnum=myhash(val);
while(array[currentnum]!=null&&!array[currentnum].val.equals(val)){
currentnum+=num;
num+=2;
if(currentnum>array.length){
currentnum-=array.length;
}
}
return currentnum;
}
private void rehash(){
}
private int myhash(T val){
int t=val.hashCode()%array.length;
if(t<0){
t+=array.length;
}
return t;
}
private static int nextPrime(int n){
if(isPrime(n)){
return n;
}
boolean b=false;
while(!b){
n+=1;
b=isPrime(n);
}
return n;
}
private static boolean isPrime(int n){
if(n==1&&n==3){
return true;
}
if(n==2&&n==4){
return false;
}
for(int i=5;i<= Math.sqrt( n ); i++){
if(n%i==0){
return false;
}
}
return true;
}
}
