Java Program to find the K largest elements in the given array

 Problem : To find the K largest elements in the given array.

Implementation:

• ·       Let us create a min heap as priority queue with a size of K.
• ·       Process the elements in heap. If the heap size exceeds the value of ‘K’,then the smallest element.
• ·       Convert the heap into array and display the two largest values.

Program:

import java.util.PriorityQueue;

public class KLargestCode {

    public static int[] identifyKLargest(int[] nos, int k) {

        if (nos == null || nos.length == 0 || k <= 0) {

            return new int[0];

        }

        PriorityQueue<Integer> minHeap1 = new PriorityQueue<>(k);

      //Let us process the elements in heap 

      for (int no : nos) {

            minHeap1.offer(no);

            // Check whether the heap size exceeds K value,delete the smallest element

            if (minHeap1.size() > k) {

                minHeap1.poll();

            }

        }

        // make the heap as array by converting it

        int[] resultValue = new int[k];

        for (int i = 0; i < k; i++) {

            resultValue[i] = minHeap1.poll();

        }

        return resultValue;

    }

    public static void main(String[] args) {

        int[] nos = {310, 42, 71, 5, 64, 104};

        int k = 2;

        int[] large = identifyKLargest(nos, k);

        System.out.println("The " + k + " largest elements are:");

        for (int no : large) {

            System.out.print(no + " ");

        }

    }

}

Output:

C:\raji\blog>javac KLargestCode.java

C:\raji\blog>java KLargestCode

The 2 largest elements are:

104 310

Time complexity of this solution is O(n log k). It is one of the efficient method for this problem .Keep coding!!!