Kth Element using HEAP (Priority queue).java

// Java code for k largest/ smallest elements in an array
import java.util.*;

class GFG {

	// Function to find k largest array element
	static void kLargest(int a[], int n, int k)
	{
		// Implementation using
		// a Priority Queue
		PriorityQueue<Integer> pq
			= new PriorityQueue<Integer>();

		for (int i = 0; i < n; ++i) {

			// Insert elements into
			// the priority queue
			pq.add(a[i]);

			// If size of the priority
			// queue exceeds k
			if (pq.size() > k) {
				pq.poll();
			}
		}

		// Print the k largest element
		while (!pq.isEmpty()) {
			System.out.print(pq.peek() + " ");
			pq.poll();
		}
		System.out.println();
	}

	// Function to find k smallest array element
	static void kSmallest(int a[], int n, int k)
	{
		// Implementation using
		// a Priority Queue
		PriorityQueue<Integer> pq
			= new PriorityQueue<Integer>(
				Collections.reverseOrder());

		for (int i = 0; i < n; ++i) {

			// Insert elements into
			// the priority queue
			pq.add(a[i]);

			// If size of the priority
			// queue exceeds k
			if (pq.size() > k) {
				pq.poll();
			}
		}

		// Print the k largest element
		while (!pq.isEmpty()) {
			System.out.print(pq.peek() + " ");
			pq.poll();
		}
	}

	// Driver Code
	public static void main(String[] args)
	{
		int a[]
			= { 11, 3, 2, 1, 15, 5, 4, 45, 88, 96, 50, 45 };
		int n = a.length;
		int k = 3;
		System.out.print(k + " largest elements are : ");
		// Function Call
		kLargest(a, n, k);
		System.out.print(k + " smallest elements are : ");
		// Function Call
		kSmallest(a, n, k);
	}
}

// This code is contributed by Harsh