K Largest Element

Posted: 30 Dec, 2020
Difficulty: Moderate

PROBLEM STATEMENT

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You are given an unsorted array containing ‘N’ integers. You need to find ‘K’ largest elements from the given array. Also, you need to return the elements in non-decreasing order.

Input Format:
The first line of the input contains an integer ‘T’ denoting the number of test cases.

The first line of each test case contains two space-separated positive integers ‘N’ and ‘K’ denoting the number of the elements present in the array and count of the largest elements you need to return as the answer respectively.

The second line of each test case contains ‘N’ space-separated integers denoting the elements of the array.
Output Format:
The only line of output of each test case should contain  ‘K’ largest elements in the array in non-decreasing order.

Print the output of each test case in a separate line.
Note:
You do not need to print anything, it has already been taken care of. Just implement the given function.
Follow Up:
Can you solve this in less than O(N*log(N)) time complexity?
Constraints:
1 <= T <= 100
1 <= N <= 10^4  
1<= K <= N  
-10^9 <= ARR[i] <= 10^9

Where ‘T’ is the number of test cases, ‘N’ is the size of the array, ‘K’ is the number of elements you need to return as an answer and ARR[i] is the size of the array of elements.

Time Limit: 1 sec
Approach 1
  • We can use bubble sort or any other sorting algorithm with some changes to solve this problem.
  • In bubble sort we have two loops:- inner loop for swapping the elements and take the highest element to the end of the remaining unsorted array and an outer loop for performing that operation ‘N’ so that array becomes sorted.
  • If we run the outer loop for ‘K’ times then we have ‘K’ largest element at the end of the array. Thus we simply take those ‘K’ elements and return them because they are already sorted in non-decreasing order as well.
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