Chocolate distribution problem GFG

//{ Driver Code Starts

//Initial Template for Java

import java.io.*;

import java.util.*;

class GfG

{

    public static void main (String[] args)

    {

        

        Scanner sc = new Scanner(System.in);

        int t = sc.nextInt();

        

        while(t-- > 0)

        {

            int n = sc.nextInt();

            ArrayList<Integer> arr = new ArrayList<>();

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

                {

                    int x = sc.nextInt();

                    arr.add(x);

                }

            int m = sc.nextInt();

            

            Solution ob = new Solution();

            

    		System.out.println(ob.findMinDiff(arr,n,m));        }

        

    }

}

// } Driver Code Ends

//User function Template for Java

class Solution

{

    public long findMinDiff (ArrayList<Integer> a, int n, int m)

    {

       if(m==0 || n==0){

           return 0;

       }

       if(n<m){

           return -1;

       }

       Collections.sort(a);

       int min = a.get(a.size()-1);

       int minUpto;

      for(int i = 0;i + m - 1 < n;i++){

          minUpto=a.get(i+m-1)-a.get(i);

          if(minUpto<min){

              min=minUpto;

          }

          

      }

       return min;

    }

}