Add solution #2006

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,682 LeetCode solutions in JavaScript
+# 1,683 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1538,6 +1538,7 @@
 2001|[Number of Pairs of Interchangeable Rectangles](./solutions/2001-number-of-pairs-of-interchangeable-rectangles.js)|Medium|
 2002|[Maximum Product of the Length of Two Palindromic Subsequences](./solutions/2002-maximum-product-of-the-length-of-two-palindromic-subsequences.js)|Medium|
 2003|[Smallest Missing Genetic Value in Each Subtree](./solutions/2003-smallest-missing-genetic-value-in-each-subtree.js)|Hard|
+2006|[Count Number of Pairs With Absolute Difference K](./solutions/2006-count-number-of-pairs-with-absolute-difference-k.js)|Easy|
 2011|[Final Value of Variable After Performing Operations](./solutions/2011-final-value-of-variable-after-performing-operations.js)|Easy|
 2016|[Maximum Difference Between Increasing Elements](./solutions/2016-maximum-difference-between-increasing-elements.js)|Easy|
 2017|[Grid Game](./solutions/2017-grid-game.js)|Medium|

solutions/2006-count-number-of-pairs-with-absolute-difference-k.js

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+/**
+ * 2006. Count Number of Pairs With Absolute Difference K
+ * https://leetcode.com/problems/count-number-of-pairs-with-absolute-difference-k/
+ * Difficulty: Easy
+ *
+ * Given an integer array nums and an integer k, return the number of pairs (i, j) where
+ * i < j such that |nums[i] - nums[j]| == k.
+ *
+ * The value of |x| is defined as:
+ * - x if x >= 0.
+ * - -x if x < 0.
+ */
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+var countKDifference = function(nums, k) {
+  const map = new Map();
+  let result = 0;
+
+  for (const num of nums) {
+    result += (map.get(num - k) || 0) + (map.get(num + k) || 0);
+    map.set(num, (map.get(num) || 0) + 1);
+  }
+
+  return result;
+};