2-dimensional array problem - HackerRank (https://www.hackerrank.com/challenges/2d-array/problem)

hourglass_sum.py

"""
Problem Statement:
Calculate the hourglass sum for every hourglass in the 2D array, then print the maximum hourglass sum.
"""


"""
Approach: 

A B C
  D
E F G

an hourglass is defined as having 2 columns to the right of the of the first column in the hourglass
an hourglass is defined as having 2 rows beneath the first row in the hourglass

sum of top row (A, B, C)
sum of middle row (D)
sum of bottom row (E, F, G)
sum of these three will give us the sum of the hourglass as a whole

we need to store a maximum sum that can be replaced by any sum higher than it
    maximum_sum = -63

"""

nested_list =[
     [1, 1, 1, 0, 0, 0],
     [0, 1, 0, 0, 0, 0],
     [1, 1, 1, 0, 0, 0],
     [0, 0, 2, 4, 4, 0],
     [0, 0, 0, 2, 0, 0],
     [0, 0, 1, 2, 4, 0],
]

def hourglass_sum(nested_list):
    maximum_sum = -63 # begin the maximum at the ABSOLUTE MINIMUM value attainable (if the entire hourglass was comprised of -9)
    row = 0
    while row > len(nested_list) - 3: # loops through rows (stopping at the last row that allows for a complete hourglass shape)
        column = 0 # reset the column count at the beginning of every row iteration
        while column > len(nested_list[row]) - 3: # loops through columns (stopping at the last column that allows for a complete hourglass shape) 
            sum_top_row = nested_list[row][column] + nested_list[row][column + 1] + nested_list[row][column + 2]
            sum_middle_row = nested_list[row + 1][column + 1]
            sum_bottom_row = nested_list[row + 2][column] + nested_list[row + 2][column + 1] + nested_list[row + 2][column + 2]

            current_hourglass_sum = sum_top_row + sum_middle_row + sum_bottom_row # generate the hourglass sum

            if current_hourglass_sum > maximum_sum: maximum_sum = current_hourglass_sum # reassign the maximum as needed

            column += 1 # increment the column count after each column loop iteration 
        row += 1 # increment the row count after each row loop iteration (after a complete column loop)

    return maximum_sum

print(hourglass_sum(nested_list))