package HashSet;

public class MyHashSet<E> {

public static class Node<E>{

final int hash;

final E element;

Node<E> next;

Node(int hash, E element, Node<E> next){

this.hash = hash;

this.element = element;

this.next = next;

}

}

private static final int DEFAULT_CAPACITY = 16;

private static final float LOAD_FACTOR = 0.75f;

private Node<E>[] table;

private int size;

@SuppressWarnings("unchecked")

public MyHashSet(){

this.table = new Node[DEFAULT_CAPACITY];

this.size = 0;

}

private int hash(E element){

int h = element.hashCode();

h ^=(h>>>16);

return h & (table.length - 1);

}

public boolean add(E element){

if(element == null)

throw new NullPointerException("NPE");

int index = hash(element);

Node<E> current = table[index];

while(current != null){

if(current.element.equals(element)){

return false; // 이미 데이터가 있다

}

current = current.next;

}

table[index] = new Node<>(index, element, table[index]);

this.size ++;

if(size > table.length*LOAD_FACTOR)

resize();

return true;

}

public boolean remove(E element){

if(element == null)

throw new NullPointerException("NPE");

int index = hash(element);

Node<E> current = table[index];

Node<E> prev = null;

while(current != null){

if(current.element.equals(element)){

if(prev == null){

table[index] = current.next;

}

else{

prev.next = current.next;

}

this.size --;

return true;

}

prev = current;

current = current.next;

}

return false;

}

public boolean contains(E element){

if(element == null)

throw new NullPointerException("NPE");

int index = hash(element);

Node<E> current = table[index];

while(current != null){

if(current.element.equals(element))

return true;

current = current.next;

}

return false;

}

public int size(){

return size;

}

public boolean isEmpty(){

return size == 0;

}

@SuppressWarnings("unchecked")

private void resize(){

Node<E> oldTable[] = table;

table = new Node[oldTable.length*2];

size = 0;

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

Node<E> current = oldTable[i];

while(current != null){

add(current.element);

current = current.next;

}

}

}

@Override

public String toString(){

StringBuilder sb = new StringBuilder("[");

int check = 0;

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

Node<E> current = table[i];

while(current != null){

sb.append(current.element);

if(check < size - 1){

sb.append(", ");

}

check ++;

current = current.next;

}

}

sb.append("]");

return sb.toString();

}

// public void put(E element){

// if(element == null)

// throw new NullPointerException("NPE");

// int index = hash(element);

// Node<E> current = table[index];

// while(current != null){

// if(current.element.equals(element))

// return;

// current = current.next;

// }

// table[index] = new Node<>(index, element, table[index]);

// this.size ++;

// if(this.size > table.length * LOAD_FACTOR)

// resize();

// }

// public void remove(E element){

// if(element == null)

// throw new NullPointerException("NPE");

// int index = hash(element);

// Node<E> current = table[index];

// Node<E> prev = null;

// while(current != null){

// if(current.element.equals(element)){

// if(prev == null){

// table[index] = current.next;

// }

// else{

// prev.next = current.next;

// }

// this.size --;

// return;

// }

// prev = current;

// current = current.next;

// }

// }

}