public class Heap<T extends Comparable<T>>{
  public T[] heap;
  public int SIZE;
  public int count;

  Heap(int size){
    SIZE = size;
    // reference: https://stackoverflow.com/questions/34827626/cannot-be-cast-to-ljava-lang-comparable
    heap = (T[])new Comparable[SIZE];
    count = 0;
  }

  
  public void add (T item){
    if(count >= SIZE){
      // throw new Exception("Heap Overflow");
      System.out.println("Heap Full");
      return;
    }
   
    // for (int i=0;i<SIZE;i++){
    //   if(heap[i]==null){
    //     count=i;
    //     heap[count] = item;
    //   }
    //   else if{
        
    //   }
      
    // }
    heap[count]=item;
    percolateUp(count);
    count++;
  }
  private void percolateUp(int count) {
    
    while(0  < count){
      int j = (count - 1) / 2;
      
      int arr=heap[count].compareTo(heap[j]);
      if(arr<0){
        break;
      }
      swap(count, j);
      count = j;
    }
  }
  public void swap(int i, int j){
    T temp = heap[i];
    heap[i] = heap[j];
    heap[j] = temp;
  }

  public T delete(){
    T temp = heap[0];
    heap[0] = heap[--count];
    percolateDown(count, 0);
    heap[count] = null;
    return temp;
  }
  private int percolateDown(int count, int i) {
      int j;
      while(i != (j = ProperParent(count, i))){
        swap(i, j);
        i = j;
      }
      return i;
  }
  private int ProperParent(int count, int i) {
    return RChildValid(count, i) ? Bigger(Bigger(i,  i * 2 + 1), i * 2 + 2) :
            LChildValid(count, i) ? Bigger(i, i * 2 + 1) : i;
  }
  public boolean RChildValid(int n, int i){
    if(i * 2 + 2 < n){
      return true;
    }
    return false;
  }
  public boolean LChildValid(int n, int i){
    if(i * 2 + 1 < n){
      return true;
    }
    return false;
  }
  public int Bigger(int i, int j){
    
    int arr=heap[i].compareTo(heap[j]);
    if(j < count){
      return arr>0 ? i : j;
    }
    return i;
  }

  public void print(){
    for(int i=0;i<SIZE;i++){
      System.out.print(heap[i]+"  ");
    }
  }
  public static void main(String[] args) {
    //int a[] ={5,7,10,3,15,8,20,18};
    Heap<Integer> heap = new Heap<Integer>(10);
    heap.add(1);
    heap.print();
    System.out.println(" ");
    heap.add(2);
    heap.print();
    System.out.println(" ");
    heap.add(3);
    heap.print();
    System.out.println(" ");
    heap.add(5);
    heap.print();
    System.out.println(" ");
    heap.add(4);
    heap.print();
    System.out.println(" ");
    heap.add(10);
    heap.print();
    System.out.println(" ");
    heap.delete();
    heap.print();
    
  }  
  
}