refactor: improve maxSubArray implementation

- Enhance code readability with clearer variable names
- Add detailed docstring for function explanation
- Maintain functionality while optimizing structure

Author: sounmind

maximum-subarray/sounmind.py

@@ -3,11 +3,24 @@
 
 class Solution:
     def maxSubArray(self, nums: List[int]) -> int:
-        global_max_sum = nums[0]
-        local_max_sum = nums[0]
-        
+        """
+        Find the contiguous subarray with the largest sum using Kadane's algorithm.
+
+        Args:
+            nums: List of integers
+
+        Returns:
+            Maximum subarray sum
+        """
+        if not nums:
+            return 0
+
+        global_max = local_max = nums[0]
+
         for num in nums[1:]:
-            local_max_sum = max(num, local_max_sum + num)
-            global_max_sum = max(global_max_sum, local_max_sum)
+            # Either start a new subarray with current element or extend previous subarray
+            local_max = max(num, local_max + num)
+            # Update global maximum if current local maximum is greater
+            global_max = max(global_max, local_max)
 
-        return global_max_sum
+        return global_max