package com.thealgorithms.datastructures.heaps;

import java.util.*;

public class GenericHeap <T extends Comparable <T> >{
	ArrayList <T> data=new ArrayList<>();
	HashMap<T,Integer> map=new HashMap<>();
	public void add(T item) {
		this.data.add(item);
		map.put(item,this.data.size()-1);//
		upHeapify(this.data.size()-1);
	}
	private void upHeapify(int ci) {
		int pi=(ci-1)/2;
		if(isLarger(this.data.get(ci),this.data.get(pi))>0) {
			swap(pi,ci);
			upHeapify(pi);
		}
	}
	public void display() {
		System.out.println(this.data);
	}
	public int size() {
		return this.data.size();
	}
	public boolean isEmpty() {
		return this.size()==0;
	}
	public T remove() {
		this.swap(0,this.size()-1);
		T rv=this.data.remove(this.size()-1);
		downHeapify(0);
		map.remove(rv); 
		return rv;
	}
	private void downHeapify(int pi) {
		int lci=2*pi+1;
		int rci=2*pi+2;
		int mini=pi;
		if(lci<this.size() &&  isLarger(this.data.get(lci),this.data.get(mini))>0) {
			mini=lci;
		}
		if(rci<this.size() &&  isLarger(this.data.get(rci),this.data.get(mini))>0) {
			mini=rci;
		}
		if(mini!=pi) {
			this.swap(pi,mini);
			downHeapify(mini);
		}
	}
	public T get() {
		return this.data.get(0);
	}
	//t has higher property then return +ve
	private int isLarger(T t,T o) {
		return t.compareTo(o);
	}
	private void swap(int i,int j) {
		T ith=this.data.get(i);
		T jth=this.data.get(j);
		this.data.set(i,jth);
		this.data.set(j,ith);
		map.put(ith,j);
		map.put(jth,i);
	}
	public void updatePriority(T item) {
		int index=map.get(item);
		//because we enter lesser value then old vale
		upHeapify(index);
	}
}