feat: add Two Sum

Author: dukeluo

README.md

@@ -10,3 +10,4 @@ https://neetcode.io/roadmap
 | --- | ----------------------------------------------------------------------- | ---------- | ---------------------------------------------------- |
 | 217 | [Contains Duplicate](https://leetcode.com/problems/contains-duplicate/) | Easy       | [TypeScript](./TypeScript/217.contains-duplicate.ts) |
 | 242 | [Valid Anagram](https://leetcode.com/problems/valid-anagram/)           | Easy       | [TypeScript](./TypeScript/242.valid-anagram.ts)      |
+| 242 | [Two Sum](https://leetcode.com/problems/two-sum/)                       | Easy       | [TypeScript](./TypeScript/1.two-sum.ts)              |

TypeScript/1.two-sum.ts

@@ -0,0 +1,13 @@
+function twoSum(nums: number[], target: number): number[] {
+  const map = new Map<number, number>();
+
+  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);
+  }
+
+  return [-1, -1];
+}