solves count number of pairs with absolut difference k

Author: anishLearnsToCode

README.md

@@ -479,7 +479,7 @@
 | 1991 | [Find the Middle Index in Array](https://leetcode.com/problems/find-the-middle-index-in-array)                                                            |                                                            [![Java](assets/java.png)](src/FindTheMiddleIndexInArray.java)                                                            |                                                                                                                                   |
 | 1995 | [Count Special Quadruplets](https://leetcode.com/problems/count-special-quadruplets)                                                                      |                                                             [![Java](assets/java.png)](src/CountSpecialQuadruplets.java)                                                             |                                                                                                                                   |
 | 2000 | [Reverse Prefix of Word](https://leetcode.com/problems/reverse-prefix-of-word)                                                                            |                                                               [![Java](assets/java.png)](src/ReversePrefixOfWord.java)                                                               |                                                                                                                                   |
-| 2006 | [Count Number of Pairs With Absolute Difference K](https://leetcode.com/problems/count-number-of-pairs-with-absolute-difference-k)                        |                                                                                                                                                                                      |                                                                                                                                   |
+| 2006 | [Count Number of Pairs With Absolute Difference K](https://leetcode.com/problems/count-number-of-pairs-with-absolute-difference-k)                        |                                                    [![Java](assets/java.png)](src/CountNumberOfPairsWithAbsoluteDifferenceK.java)                                                    |                                                                                                                                   |
 | 2011 | [Final Value of Variable After Performing Operations](https://leetcode.com/problems/final-value-of-variable-after-performing-operations)                  |                                                                                                                                                                                      |                                                                                                                                   |
 | 2016 | [Maximum Difference Between Increasing Elements](https://leetcode.com/problems/maximum-difference-between-increasing-elements)                            |                                                                                                                                                                                      |                                                                                                                                   |
 | 2022 | [Convert 1D Array Into 2D Array](https://leetcode.com/problems/convert-1d-array-into-2d-array)                                                            |                                                                                                                                                                                      |                                                                                                                                   |

src/CountNumberOfPairsWithAbsoluteDifferenceK.java

@@ -0,0 +1,19 @@
+// https://leetcode.com/problems/count-number-of-pairs-with-absolute-difference-k
+// T: O(N)
+// S: O(N)
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class CountNumberOfPairsWithAbsoluteDifferenceK {
+    public int countKDifference(int[] nums, int k) {
+        final Map<Integer, Integer> frequency = new HashMap<>();
+        int pairs = 0;
+        for (int element : nums) {
+            pairs += frequency.getOrDefault(element - k, 0);
+            pairs += frequency.getOrDefault(element + k, 0);
+            frequency.put(element, frequency.getOrDefault(element, 0) + 1);
+        }
+        return pairs;
+    }
+}