Add solution #340

Author: JoshCrozier

README.md

@@ -328,6 +328,7 @@
 337|[House Robber III](./solutions/0337-house-robber-iii.js)|Medium|
 338|[Counting Bits](./solutions/0338-counting-bits.js)|Easy|
 339|[Nested List Weight Sum](./solutions/0339-nested-list-weight-sum.js)|Medium|
+340|[Longest Substring with At Most K Distinct Characters](./solutions/0340-longest-substring-with-at-most-k-distinct-characters.js)|Medium|
 341|[Flatten Nested List Iterator](./solutions/0341-flatten-nested-list-iterator.js)|Medium|
 342|[Power of Four](./solutions/0342-power-of-four.js)|Easy|
 343|[Integer Break](./solutions/0343-integer-break.js)|Medium|

solutions/0340-longest-substring-with-at-most-k-distinct-characters.js

@@ -0,0 +1,35 @@
+/**
+ * 340. Longest Substring with At Most K Distinct Characters
+ * https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/
+ * Difficulty: Medium
+ *
+ * Given a string s and an integer k, return the length of the longest substring of s that
+ * contains at most k distinct characters.
+ */
+
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+var lengthOfLongestSubstringKDistinct = function(s, k) {
+  const map = new Map();
+  let result = 0;
+  let left = 0;
+
+  for (let right = 0; right < s.length; right++) {
+    map.set(s[right], (map.get(s[right]) || 0) + 1);
+
+    while (map.size > k) {
+      map.set(s[left], map.get(s[left]) - 1);
+      if (map.get(s[left]) === 0) {
+        map.delete(s[left]);
+      }
+      left++;
+    }
+
+    result = Math.max(result, right - left + 1);
+  }
+
+  return result;
+};