Createheap.java

package Heap;

import java.util.ArrayList;

public class Createheap {
    static class Heap{
        ArrayList<Integer> arr=new ArrayList<>();

        public void add(int data){
            arr.add(data);

            int x=arr.size()-1;//x is child index
            int par=(x-1)/2;//par index

            while(arr.get(x)<arr.get(par)){
                //swap
                int temp=arr.get(x);
                arr.set(x,arr.get(par));
                arr.set(par,temp);
                x=par;
                par=(x-1)/2;
            }
        }
        public int peek(){
            return arr.get(0);
        }
        private void heapify(int i){
            int left=2*i+1;
            int right = 2*i+2;
            int minIdx=i;

            if(left<arr.size() && arr.get(minIdx)>arr.get(left)){
                minIdx=left;
            }
            if(right<arr.size() && arr.get(minIdx)>arr.get(right)){
                minIdx=right;
            }
            if(minIdx!=i){
                //swap
                int temp=arr.get(i);
                arr.set(i,arr.get(minIdx));
                arr.set(minIdx,temp);
                heapify(minIdx);
            }

        }
        public  int remove(){
            int data=arr.get(0);

            int temp=arr.get(0);
            arr.set(0,arr.get(arr.size()-1));
            arr.set(arr.size()-1,temp);

            arr.remove(arr.size()-1);
            
            heapify(0);
            return data;
        }
        public boolean isEmpty(){
            return arr.size()==0;
        }
    }

    public static void main(String[] args) {
        Heap h=new Heap();
        h.add(4);
        h.add(3);
       
        h.add(1);
        h.add(5);
       

        while(!h.isEmpty()){
            System.out.println(h.peek());
            h.remove();
        }
    }
    
}