Leetcode problem 61 - Count the Number of Consistent Strings

You are given a string allowed consisting of distinct characters and an array of strings words. A string is consistent if all characters in the string appear in the string allowed.

Return the number of consistent strings in the array words.

Example 1:

Input: allowed = “ab”, words = [“ad”,”bd”,”aaab”,”baa”,”badab”] Output: 2 Explanation: Strings “aaab” and “baa” are consistent since they only contain characters ‘a’ and ‘b’. Example 2:

Input: allowed = “abc”, words = [“a”,”b”,”c”,”ab”,”ac”,”bc”,”abc”] Output: 7 Explanation: All strings are consistent. Example 3:

Input: allowed = “cad”, words = [“cc”,”acd”,”b”,”ba”,”bac”,”bad”,”ac”,”d”] Output: 4 Explanation: Strings “cc”, “acd”, “ac”, and “d” are consistent.

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var countKDifference = function (nums, k) {
  //  Create a hash table to store the elements from the nums array.
  let hash = {};
  // Initialize a count variable with the value 0.
  let count = 0;

  // Iterate through nums array using a for loop
  for (let num of nums) {
    // For each element nums[i], check if map contains an element where the current element is reduced by the 'k' value.
    if (num in hash) {
      // If so, increment count value.
      hash[num] += 1;
    } else {
      // Set the current element in map
      hash[num] = 1;
    }
  }
  //  Iterate through nums array using a for loop
  for (let num of nums) {
    // For each element nums[i], check if map contains an element where the current element is reduced by the 'k' value.
    if (num - k in hash) {
      // If so, increment count value.
      count += hash[num - k];
    }
  }
  // return count
  return count;
};