#2006 - Count Number of Pairs With Absolute Difference K

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Problem Description

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.

Solution

/**
 * @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;
};