m0s3bry

"""
Maximum Subarray (Kadane's Algorithm)
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Provides two APIs:
  - max_subarray_sum(nums): returns the maximum subarray sum (int)
  - max_subarray_with_indices(nums): returns (max_sum, start_idx, end_idx) inclusive

Both handle all-negative arrays correctly. Empty input raises ValueError.
Time: O(n), Space: O(1).