Merge pull request neetcode-gh#26 from chandra9302/patch-3

Create 1-Two-Sum.swift

Author: neetcode-gh

swift/1-Two-Sum.swift

@@ -0,0 +1,18 @@
+/**
+ * Question Link: https://leetcode.com/problems/two-sum/
+ */
+
+class TwoSum {
+    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+        var prevMap = [Int:Int]() // val -> index
+        
+        for (i, n) in nums.enumerated() {
+            let diff = target - n
+            if let firstIndex = prevMap[diff] {
+                return [firstIndex, i]
+            }
+            prevMap[n] = i
+        }
+        return []
+    }
+}