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import java.util.ArrayList;

import java.util.LinkedList;

public class HashMap<K,V> {

public class hmnodes{ //HashMap nodes

K key;

V value;

}

private int size=0; //size of hashmap

private LinkedList<hmnodes> buckets[]; //array of addresses of list

public HashMap(){

buckets=new LinkedList[4]; //initially create bucket of any size

for(int i=0;i<4;i++)

buckets[i]=new LinkedList<>();

}

public void put(K key,V value) throws Exception{

int bi=bucketIndex(key); //find the index,the new key will be inserted in linklist at that index

int fountAt=find(bi,key); //check if key already exists or not

if(fountAt==-1){

hmnodes temp=new hmnodes(); //if doesn't exist create new node and insert

temp.key=key;

temp.value=value;

buckets[bi].addLast(temp);

this.size++;

}else{

buckets[bi].get(fountAt).value=value;//if already exist modify the value

}

double lambda = (this.size*1.0)/this.buckets.length;

if(lambda>2.0){

rehash(); //rehashing function which will increase the size of bucket as soon as lambda exceeds 2.0

}

return;

}

public V get(K key) throws Exception{

int bi=bucketIndex(key);

int fountAt=find(bi,key);

if(fountAt==-1){

return null;

}else{

return buckets[bi].get(fountAt).value;

}

}

public V remove(K key) throws Exception{

int bi=bucketIndex(key);

int fountAt=find(bi,key);

if(fountAt==-1){

return null;

}else{

this.size--;

return buckets[bi].remove(fountAt).value;

}

}

public boolean containskey(K key) throws Exception{

int bi=bucketIndex(key);

int fountAt=find(bi,key);

if(fountAt==-1){

return false;

}else{

return true;

}

}

public int size(){

return this.size;

}

public boolean isempty(){

return this.size==0;

}

public ArrayList<K> keyset() throws Exception{

ArrayList<K> arr=new ArrayList<>();

for(int i=0;i<buckets.length;i++){

for(int j=0;j<buckets[i].size();j++){

arr.add(buckets[i].get(j).key);

}

}

return arr;

}

public ArrayList<V> valueset() throws Exception{

ArrayList<V> arr=new ArrayList<>();

for(int i=0;i<buckets.length;i++){

for(int j=0;j<buckets[i].size();j++){

arr.add(buckets[i].get(j).value);

}

}

return arr;

}

public void display() throws Exception{

for(int i=0;i<buckets.length;i++){

System.out.print("Bucket: "+i+" ");

for(int j=0;j<buckets[i].size();j++){

hmnodes temp=buckets[i].get(j);

System.out.print("["+temp.key+"->"+temp.value+"]");

}

System.out.println();

}

}

public int find(int bi,K key) throws Exception{

for(int i=0;i<buckets[bi].size();i++){

if(key.equals(buckets[bi].get(i).key))

return i;

}

return -1;

}

public int bucketIndex(K key) throws Exception{

int bi=key.hashCode();

return Math.abs(bi%buckets.length);

}

private void rehash() throws Exception{

LinkedList<hmnodes> ob[]= buckets;

buckets=new LinkedList[ob.length*2];

for(int i=0;i<ob.length*2;i++)

buckets[i]=new LinkedList<>();

size = 0;

for(int i=0;i<ob.length;i++){

for(int j=0;j<ob[i].size();j++){

put(ob[i].get(j).key,ob[i].get(j).value);

}

}

}

}