Updated matrix method, brute force, time complexity is 2n

[danimetz]

Time Complexity: O(n^2)
Space Complexity: O(2n)

[shrutivanw]

Nice work!

Since the problem statement encouraged you to optimize the space complexity as much as possible, can you think of how you could tweak your algorithm to have a space complexity of O(1)? Once you have given it some more thought, tally your solution with mine here: https://github.com/Ada-C10/matrix_check_sum/blob/solution/lib/matrix_check_sum.rb