Add comment to two-sum

Author: delight010

two-sum/delight010.swift

@@ -2,6 +2,7 @@ class Solution {
     func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
         var dictionary: [Int: Int] = [:]
         for (index, value) in nums.enumerated() {
+            // nums배열의 개수만큼 반복합니다. O(n)
             let difference = target - value
             if let otherIndex = dictionary[difference] {
                 return [otherIndex, index]