printing out the elements in a box in a Sudoku board

Question

for example, I have a 9x9 sudoku board like this:

big = [[0, 0, 0, 0, 0, 0, 0, 0, 0],
   [4, 0, 0, 7, 8, 9, 0, 0, 0],
   [7, 8, 0, 0, 0, 0, 0, 5, 6],
   [0, 2, 0, 3, 6, 0, 8, 0, 0],
   [0, 0, 5, 0, 0, 7, 0, 1, 0],
   [8, 0, 0, 2, 0, 0, 0, 0, 5],
   [0, 0, 1, 6, 4, 0, 9, 7, 0],
   [0, 0, 0, 9, 0, 0, 0, 0, 0],
   [0, 0, 0, 0, 3, 0, 0, 0, 2]]

and I have a function: def subgrid_values(board,r,c) board takes in the size of the board which in this case is big. r takes in the row and c takes in the column.

so if I input subgrid_values(big,4,5) it will give me an output of [3,6,7,2]

I'm trying to output that list but I do not know how to

I hope this makes it clearer.

Answer 1

One of the solutions would be to get the starting index of the sub-grid and loop three times on row and column as follows:

def solution(big, r, c):
  output = []
  row_start_index = (r // 3) * 3
  col_start_index = (c // 3) * 3

  for ri in range(row_start_index, row_start_index + 3):
    for ci in range(col_start_index, col_start_index + 3):
      if big[ri][ci]:
        output.append(big[ri][ci])
  return output