Add maximum subarray sum (Kadane's Algorithm) code

[ydvmudit07]

Closes #143

This pull request implements the maximum subarray sum algorithm, also known as Kadane's algorithm.

Changes:

• Added max_subarray_sum() function
• Initializes variables to track maximum sum ending at current position and maximum seen so far
• Iterates through array, calculating max ending at current position
• Compares with max seen so far and updates
• Returns overall maximum subarray sum

This algorithm efficiently finds the contiguous subarray with the largest sum within a given array. I have added tests to validate the implementation with different input cases. @himanshu-03 , please review the code changes and let me know if anything needs to be updated or improved. I'm happy to make revisions to ensure this algorithm is accurately and efficiently implemented.

Looking forward to getting this useful algorithm merged to the codebase under the hacktoberfest tag!

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[himanshu-03]

I believe that kadanes algorithm should not be placed in algorithm directory. Take a look around the repo and see if it can fit around already defined directories.

[ydvmudit07]

Sure I'll do it, thanks for letting me know.

[ydvmudit07]

@himanshu-03 , based on the existing folder structure of the Python DSA repository, I just added the Kadane's algorithm implementation in the "Math" folder.

The Kadane's algorithm involves finding the maximum subarray sum within an array using mathematical logic and comparisons. Since it is more of a mathematical algorithm rather than a specific data structure or technique, the "Math" folder seems like the best fit.

Let me know if you need any other specific folder name recommendations or have additional context to consider
Kindly review and merge it under the tag "hacktoberfest"!

[himanshu-03]

LGTM!

[himanshu-03]

Great job!
Thank you for contributing. Do give this repository a star if you feel like ✨️