Add solution #621

Author: JoshCrozier

README.md

@@ -223,6 +223,7 @@
 605|[Can Place Flowers](./0605-can-place-flowers.js)|Easy|
 606|[Construct String from Binary Tree](./0606-construct-string-from-binary-tree.js)|Easy|
 617|[Merge Two Binary Trees](./0617-merge-two-binary-trees.js)|Easy|
+621|[Task Scheduler](./0621-task-scheduler.js)|Medium|
 628|[Maximum Product of Three Numbers](./0628-maximum-product-of-three-numbers.js)|Easy|
 643|[Maximum Average Subarray I](./0643-maximum-average-subarray-i.js)|Easy|
 645|[Set Mismatch](./0645-set-mismatch.js)|Medium|

solutions/0621-task-scheduler.js

@@ -0,0 +1,37 @@
+/**
+ * 621. Task Scheduler
+ * https://leetcode.com/problems/task-scheduler/
+ * Difficulty: Medium
+ *
+ * You are given an array of CPU tasks, each labeled with a letter from A to Z, and a number n.
+ * Each CPU interval can be idle or allow the completion of one task. Tasks can be completed
+ * in any order, but there's a constraint: there has to be a gap of at least n intervals
+ * between two tasks with the same label.
+ *
+ * Return the minimum number of CPU intervals required to complete all tasks.
+ */
+
+/**
+ * @param {character[]} tasks
+ * @param {number} n
+ * @return {number}
+ */
+var leastInterval = function(tasks, n) {
+  const map = new Map();
+  let maxValue = 0;
+  let maxCount = 0;
+
+  tasks.forEach(key => {
+    const value = map.has(key) ? map.get(key) + 1 : 1;
+    map.set(key, value);
+
+    if (value > maxValue) {
+      maxValue = value;
+      maxCount = 1;
+    } else if (value === maxValue) {
+      maxCount++;
+    }
+  });
+
+  return Math.max(tasks.length, (maxValue - 1) * (n + 1) + maxCount);
+};