Add maximum subarray sum (Kadane's Algorithm) code

Math/kadane's_algorithm.py

@@ -0,0 +1,17 @@
+def max_subarray_sum(nums):
+    # Initialize variables to keep track of the maximum subarray sum
+
+    max_ending_here = nums[0]  # Maximum sum ending at the current position
+    max_so_far = nums[0]  # Maximum sum seen so far
+
+    # Iterate through the array, starting from the second element
+    for i in range(1, len(nums)):
+        # Calculate the maximum sum ending at the current position by considering whether it's better to 
+        # start a new subarray or extend the previous one.
+        max_ending_here = max(nums[i], max_ending_here + nums[i])
+
+        # Update the maximum sum seen so far by comparing it with the   maximum sum ending at the current position.
+        max_so_far = max(max_so_far, max_ending_here)
+
+    # The 'max_so_far' variable now contains the maximum subarray sum.
+    return max_so_far