solves beautiful triplets

Author: anishLearnsToCode

src/implimentation/BeautifulTriplets.java

@@ -0,0 +1,41 @@
+// https://www.hackerrank.com/challenges/beautiful-triplets/problem
+
+package implimentation;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Scanner;
+
+public class BeautifulTriplets {
+    private static final Scanner scanner = new Scanner(System.in);
+
+    public static void main(String[] args) {
+        int length = scanner.nextInt();
+        int difference = scanner.nextInt();
+        int[] array = getArray(length);
+        System.out.println(beautifulTriplets(array, difference));
+    }
+
+    private static long beautifulTriplets(int[] array, int difference) {
+        Map<Integer, Integer> pairs = new HashMap<>();
+        Map<Integer, Integer> frequency = new HashMap<>();
+        frequency.put(array[array.length - 1], 1);
+        long beautifulTriplets = 0;
+        for (int index = array.length - 2 ; index >= 0 ; index--) {
+            int number = array[index];
+            pairs.put(number, pairs.getOrDefault(number, 0)
+                    + frequency.getOrDefault(number + difference, 0));
+            beautifulTriplets += pairs.getOrDefault(number + difference, 0);
+            frequency.put(number, frequency.getOrDefault(number, 0) + 1);
+        }
+        return beautifulTriplets;
+    }
+
+    private static int[] getArray(int length) {
+        int[] array = new int[length];
+        for (int index = 0 ; index < length ; index++) {
+            array[index] = scanner.nextInt();
+        }
+        return array;
+    }
+}