feat: Add solution for LeetCode problem 53

Author: WhiteHyun

maximum-subarray/WhiteHyun.swift

@@ -0,0 +1,22 @@
+//  
+//  53. Maximum Subarray
+//  https://leetcode.com/problems/maximum-subarray/description/
+//  Dale-Study
+//  
+//  Created by WhiteHyun on 2024/07/20.
+//  
+
+class Solution {
+  func maxSubArray(_ numbers: [Int]) -> Int {
+    var tracking = numbers[0]
+    var answer = numbers[0]
+    for value in numbers.dropFirst() {
+      tracking = max(tracking + value, value)
+      if tracking > answer {
+        answer = tracking
+      }
+    }
+
+    return answer
+  }
+}