Solution.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

  // Complete the beautifulTriplets function below.
  static int beautifulTriplets(int d, int[] arr) {
    HashMap<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < arr.length; i++) {
      if (map.containsKey(arr[i])) {
        map.put(arr[i], map.get(arr[i]) + 1);
      } else {
        map.put(arr[i], 1);
      }
    }

    int counter = 0;
    // i < j < k
    // find = d + a[i]
    for (int i = 0; i < arr.length; i++) {
      if (i == 0 || arr[i] != arr[i - 1]) {
        int j = d + arr[i];
        int k = d + j;
        if (map.containsKey(j) && map.containsKey(k)) {
          counter += map.get(arr[i]) * map.get(j) * map.get(k);
        }
      }
    }

    return counter;
  }

  private static final Scanner scanner = new Scanner(System.in);

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

    String[] nd = scanner.nextLine().split(" ");

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

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

    int[] arr = new int[n];

    String[] arrItems = scanner.nextLine().split(" ");
    scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

    for (int i = 0; i < n; i++) {
      int arrItem = Integer.parseInt(arrItems[i]);
      arr[i] = arrItem;
    }

    int result = beautifulTriplets(d, arr);

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

    bufferedWriter.close();

    scanner.close();
  }
}