Count_Number_of_Pairs_With_Absolute_Difference_K.js

// 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.

// Example 1:

// Input: nums = [1,2,2,1], k = 1
// Output: 4
// Explanation: The pairs with an absolute difference of 1 are:
// - [1,2,2,1]
// - [1,2,2,1]
// - [1,2,2,1]
// - [1,2,2,1]

// Example 2:

// Input: nums = [1,3], k = 3
// Output: 0
// Explanation: There are no pairs with an absolute difference of 3.

// Example 3:

// Input: nums = [3,2,1,5,4], k = 2
// Output: 3
// Explanation: The pairs with an absolute difference of 2 are:
// - [3,2,1,5,4]
// - [3,2,1,5,4]
// - [3,2,1,5,4]

// Constraints:

//     1 <= nums.length <= 200
//     1 <= nums[i] <= 100
//     1 <= k <= 99

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var countKDifference = function (nums, k) {
  let obj = {},
    count = 0;
  for (let key of nums) obj[key] = obj[key] ? obj[key] + 1 : 1;
  for (let i = 0; i < nums.length; i++) {
    if (obj[nums[i] + k]) count += obj[nums[i] + k];
  }
  return count;
};