From 450c2fa289eb93bc791d4b6f47fcff5c7f59a3ec Mon Sep 17 00:00:00 2001
From: SHEEVOOT <sheevoot@apples-MacBook-Pro.local>
Date: Fri, 11 Oct 2019 17:12:37 +0530
Subject: [PATCH] Added Two Sum problem

---
 README.md                              |  1 +
 src/_Problems_/two-sum/index.js        | 25 +++++++++++++++++++++++++
 src/_Problems_/two-sum/two-sum.test.js | 11 +++++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 src/_Problems_/two-sum/index.js
 create mode 100644 src/_Problems_/two-sum/two-sum.test.js

diff --git a/README.md b/README.md
index fd888d40..944bb70e 100644
--- a/README.md
+++ b/README.md
@@ -67,6 +67,7 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
 - [Reverse String](src/_Problems_/reverse_string)
 - [Maximum Product of Three Numbers](src/_Problems_/max-product-of-3-numbers)
 - [Next Greater for Every Element in an Array](src/_Problems_/next-greater-element)
+- [Two Sum](src/_Problems_/two-sum)
 
 ### Searching
 
diff --git a/src/_Problems_/two-sum/index.js b/src/_Problems_/two-sum/index.js
new file mode 100644
index 00000000..06dbfb44
--- /dev/null
+++ b/src/_Problems_/two-sum/index.js
@@ -0,0 +1,25 @@
+/*
+Two Sum Problem
+Given an array of integers, return indices of the two numbers such that they add up to a specific target.
+You may assume that each input would have exactly one solution, and you may not use the same element twice.
+
+Example:
+Given nums = [2, 7, 11, 15], target = 9,
+Because nums[0] + nums[1] = 2 + 7 = 9,
+return [0, 1].
+
+Solved in O(n) time complexity using Hash/Object
+*/
+
+function twoSum(nums, target) {
+    const numsHash = {};
+    for (let i = 0; i < nums.length; i++) {
+        const difference = target - nums[i];
+        if (numsHash[difference] !== undefined) {
+            return [numsHash[difference], i];
+        }
+        numsHash[nums[i]] = i;
+    }
+};
+
+module.exports = { twoSum };
\ No newline at end of file
diff --git a/src/_Problems_/two-sum/two-sum.test.js b/src/_Problems_/two-sum/two-sum.test.js
new file mode 100644
index 00000000..6af61e4e
--- /dev/null
+++ b/src/_Problems_/two-sum/two-sum.test.js
@@ -0,0 +1,11 @@
+const { twoSum } = require('.');
+
+describe('Two Sum', () => {
+    it('Should return a index of elements added to get target', () => {
+        expect(twoSum([2, 7, 11, 15], 9)).toEqual([0, 1]);
+    });
+
+    it('Should return a index of elements added to get target', () => {
+        expect(twoSum([8, -4, 2, 14, 11, 17], 7)).toEqual([1, 4]);
+    });
+});