Heap

Heap is implemented by PriorityQueue.

• Mainly 3 methods are useful peek, add, remove.
• The priority queue takes the minimum element in the peek. We can also specify to put max element in the peek.
• Heap stores the element inside it in random manner. Like hashmap we cannot be able to maintain how the element will be stored in the heap.

PriorityQueue<Integer> pq = new PriorityQueue<>();
  int[] rank = {22,11,12,8,3};
  for(int i=0;i<rank.length;i++){
     pq.add(rank[i]);
  }
  while(pq.size()>0){
      System.out.print(pq.peek()+" ");
      pq.remove();
  }

This will show the output in ascending order. The minimum element will be in the peek.

• For storing in reverse order we need to write Collections.reverseOrder().

PriorityQueue<Integer> pqRev = new PriorityQueue<>(Collections.reverseOrder());

Binary Heap.