Beautiful_Triplets.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

class Result {

    /*
     * Complete the 'beautifulTriplets' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts following parameters:
     *  1. INTEGER d
     *  2. INTEGER_ARRAY arr
     */

    public static int beautifulTriplets(int d, List<Integer> arr) 
    {
      // Write your code here
      Set<Integer> set = new HashSet<>();  //creating a set..
      int i;
      int count=0;
      //first putting each value of the "arr" list in the set..
      for(i=0;i<arr.size();i++)
      {
          set.add(arr.get(i));
      }
      //now for each value of the list "arr"..
      //check the following property..
      //difference between two numbers is same or not to the d..
      for(i=0;i<arr.size();i++)
      {
          int num = arr.get(i);  //for a particular value.
          if(set.contains(num+d) && set.contains(num+2*d))   
          {
              count++;
          }
      }
      return count; //this will tell about the number beautiful triplets..
    }
}

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        String[] firstMultipleInput = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        int n = Integer.parseInt(firstMultipleInput[0]);

        int d = Integer.parseInt(firstMultipleInput[1]);

        List<Integer> arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
            .map(Integer::parseInt)
            .collect(toList());

        int result = Result.beautifulTriplets(d, arr);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}