Add solution #1

Author: JoshCrozier

README.md

@@ -6,6 +6,7 @@
 
 |#|Title|Difficulty|
 |:---|:---|:---|
+1|[Two Sum](./0001-two-sum.js)|Easy|
 4|[Median of Two Sorted Arrays](./0004-median-of-two-sorted-arrays.js)|Hard|
 31|[Next Permutation](./0031-next-permutation.js)|Medium|
 36|[Valid Sudoku](./0036-valid-sudoku.js)|Medium|

solutions/0001-two-sum.js

@@ -0,0 +1,30 @@
+/**
+ * 1. Two Sum
+ * https://leetcode.com/problems/two-sum/
+ * Difficulty: Easy
+ *
+ * Given an array of integers `nums` and an integer `target`, return indices of the two numbers such that they add up to `target`.
+ *
+ * You may assume that each input would have exactly one solution, and you may not use the same element twice.
+ *
+ * You can return the answer in any order.
+ */
+
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function(nums, target) {
+  const map = new Map();
+
+  for (let i = 0; i < nums.length; i++) {
+    const diff = target - nums[i];
+
+    if (map.has(diff)) {
+      return [map.get(diff), i];
+    }
+
+    map.set(nums[i], i);
+  }
+};