Add solution #395

Author: JoshCrozier

README.md

@@ -184,6 +184,7 @@
 387|[First Unique Character in a String](./0387-first-unique-character-in-a-string.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|
 405|[Convert a Number to Hexadecimal](./0405-convert-a-number-to-hexadecimal.js)|Easy|
 412|[Fizz Buzz](./0412-fizz-buzz.js)|Easy|
 414|[Third Maximum Number](./0414-third-maximum-number.js)|Easy|

solutions/0395-longest-substring-with-at-least-k-repeating-characters.js

@@ -0,0 +1,24 @@
+/**
+ * 395. Longest Substring with At Least K Repeating Characters
+ * https://leetcode.com/problems/longest-substring-with-at-least-k-repeating-characters/
+ * Difficulty: Medium
+ *
+ * Given a string s and an integer k, return the length of the longest substring of s such
+ * that the frequency of each character in this substring is greater than or equal to k.
+ *
+ * If no such substring exists, return 0.
+ */
+
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+var longestSubstring = function(s, k) {
+  for (const char of Array.from(new Set(s))) {
+    if (s.match(new RegExp(char, 'g')).length < k) {
+      return Math.max(...s.split(char).map(str => longestSubstring(str, k)));
+    }
+  }
+  return s.length;
+};