K_largest_elements.cpp

/*
Problem Statement:
-----------------
Given an array Arr of N positive integers, find K largest elements from the array.  The output elements should be printed in decreasing order.

Example 1:
---------
Input:
N = 5, K = 2
Arr[] = {12, 5, 787, 1, 23}
Output: 787 23
Explanation: 1st largest element in the array is 787 and second largest is 23.

Example 2:
---------
Input:
N = 7, K = 3
Arr[] = {1, 23, 12, 9, 30, 2, 50}
Output: 50 30 23

Explanation: 3 Largest element in the array are 50, 30 and 23.

Your Task:  You don't need to read input or print anything. Your task is to complete the function kLargest() which takes the array of integers arr, 
n and k as parameters and returns an array of integers denoting the answer. The array should be in decreasing order.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(K*logK)
*/

// Link --> https://practice.geeksforgeeks.org/problems/k-largest-elements4206/1#

// Code:
class Solution{
public:	
	vector <int> kLargest(int a[], int n, int k) 
	{
	    vector <int> answer;
	    priority_queue <int> maxHeap;
	    
	    for(int i=0 ; i<n ; i++)
	        maxHeap.push(a[i]);
	   
	    for(int i=0 ; i<k ; i++)
	    {
	        answer.push_back(maxHeap.top());
	        maxHeap.pop();
	    }
	    
	    return answer;
	}

};