Add solution #229

Author: JoshCrozier

README.md

@@ -72,6 +72,7 @@
 219|[Contains Duplicate II](./0219-contains-duplicate-ii.js)|Easy|
 225|[Implement Stack using Queues](./0225-implement-stack-using-queues.js)|Easy|
 226|[Invert Binary Tree](./0226-invert-binary-tree.js)|Easy|
+229|[Majority Element II](./0229-majority-element-ii.js)|Medium|
 231|[Power of Two](./0231-power-of-two.js)|Easy|
 232|[Implement Queue using Stacks](./0232-implement-queue-using-stacks.js)|Easy|
 234|[Palindrome Linked List](./0234-palindrome-linked-list.js)|Easy|

solutions/0229-majority-element-ii.js

@@ -0,0 +1,20 @@
+/**
+ * 229. Majority Element II
+ * https://leetcode.com/problems/majority-element-ii/
+ * Difficulty: Medium
+ *
+ * Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var majorityElement = function(nums) {
+  const map = new Map();
+  nums.forEach(n => map.set(n, (map.get(n) || 0) + 1));
+
+  return [...map]
+    .filter(([key, value]) => value > nums.length / 3)
+    .map(([key]) => key);
+};