Add solution #389

Author: JoshCrozier

0389-find-the-difference.js

@@ -0,0 +1,24 @@
+/**
+ * 389. Find the Difference
+ * https://leetcode.com/problems/find-the-difference/
+ * Difficulty: Easy
+ *
+ * You are given two strings s and t.
+ *
+ * String t is generated by random shuffling string s and then add one more letter at
+ * a random position.
+ *
+ * Return the letter that was added to t.
+ */
+
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {character}
+ */
+var findTheDifference = function(s, t) {
+  const map = new Map();
+  t.split('').forEach(c => map.set(c, (map.get(c) ?? 0) + 1));
+  s.split('').forEach(c => map.set(c, map.get(c) - 1));
+  return Array.from(map).find(([letter, count]) => count)[0];
+};

README.md

@@ -182,6 +182,7 @@
 374|[Guess Number Higher or Lower](./0374-guess-number-higher-or-lower.js)|Medium|
 383|[Ransom Note](./0383-ransom-note.js)|Easy|
 387|[First Unique Character in a String](./0387-first-unique-character-in-a-string.js)|Easy|
+389|[Find the Difference](./0389-find-the-difference.js)|Easy|
 392|[Is Subsequence](./0392-is-subsequence.js)|Easy|
 394|[Decode String](./0394-decode-string.js)|Medium|
 395|[Longest Substring with At Least K Repeating Characters](./0395-longest-substring-with-at-least-k-repeating-characters.js)|Medium|