Two Sum (#5)

Author: ahcode0919

src/leetcode/README.md

@@ -0,0 +1 @@
+# Leetcode

src/leetcode/arrays/README.md

@@ -1,6 +1,7 @@
 # Arrays
 
 * [Merge Two Sorted Lists](#merge-two-sorted-lists)
+* [Two Sum](#two-sum)
 
 ## Merge Two Sorted Lists
 
@@ -39,3 +40,26 @@ export function mergeTwoLists(l1, l2) {
   return head.next;
 }
 ```
+
+## Two Sum
+
+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:
+
+`[2, 7, 11, 15], 9 -> [0, 1]`
+
+```javascript
+export function(nums, target) {
+    const map = {};
+    for (let i = 0; i < nums.length; i += 1) {
+        const comp = target - nums[i];
+        if (comp in map) {
+            return [map[comp], i]
+        }
+        map[nums[i]] = i;
+    }
+};
+```

src/leetcode/arrays/two_sum.js

@@ -0,0 +1,13 @@
+
+export default function (nums, target) {
+  const map = {};
+
+  for (let i = 0; i < nums.length; i += 1) {
+    const comp = target - nums[i];
+    if (comp in map) {
+      return [map[comp], i];
+    }
+    map[nums[i]] = i;
+  }
+  return null;
+}

tests/leetcode/two_sum.test.js

@@ -0,0 +1,5 @@
+import twoSum from '../../src/leetcode/arrays/two_sum';
+
+test('should find sum', () => {
+  expect(twoSum([2, 7, 11, 15], 9)).toEqual([0, 1]);
+});