Add solution #1748

Author: JoshCrozier

README.md

@@ -224,6 +224,7 @@
 1598|[Crawler Log Folder](./1598-crawler-log-folder.js)|Easy|
 1668|[Maximum Repeating Substring](./1668-maximum-repeating-substring.js)|Easy|
 1672|[Richest Customer Wealth](./1672-richest-customer-wealth.js)|Easy|
+1748|[Sum of Unique Elements](./1748-sum-of-unique-elements.js)|Easy|
 1780|[Check if Number is a Sum of Powers of Three](./1780-check-if-number-is-a-sum-of-powers-of-three.js)|Medium|
 1880|[Check if Word Equals Summation of Two Words](./1880-check-if-word-equals-summation-of-two-words.js)|Easy|
 1886|[Determine Whether Matrix Can Be Obtained By Rotation](./1886-determine-whether-matrix-can-be-obtained-by-rotation.js)|Easy|

solutions/1748-sum-of-unique-elements.js

@@ -0,0 +1,23 @@
+/**
+ * 1748. Sum of Unique Elements
+ * https://leetcode.com/problems/sum-of-unique-elements/
+ * Difficulty: Easy
+ *
+ * You are given an integer array nums. The unique elements of an array are the
+ * elements that appear exactly once in the array.
+ *
+ * Return the sum of all the unique elements of nums.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var sumOfUnique = function(nums) {
+  const map = new Map();
+  nums.forEach(n => map.set(n, (map.get(n) || 0) + 1));
+
+  return [...map].reduce((sum, [key, value]) => {
+    return sum + (value === 1 ? key : 0);
+  }, 0);
+};