curriculum/challenges/english/blocks/learn-classes-and-objects-by-building-a-sudoku-solver/6606cf1b2b9f65529c161098.md
Similarly to the previous step, you need to ensure that the starting column index for each 3x3 square is a multiple of 3.
Declare a variable col_start and assign it (col // 3) * 3.
You should declare a variable col_start with the value of (col // 3) * 3.
({ test: () => assert(runPython(`_Node(_code).find_class("Board").find_function("valid_in_square").find_variable("col_start").is_equivalent("col_start = (col//3)*3")`)) })
class Board:
def __init__(self, board):
self.board = board
def find_empty_cell(self):
for row, contents in enumerate(self.board):
try:
col = contents.index(0)
return row, col
except ValueError:
pass
return None
def valid_in_row(self, row, num):
return num not in self.board[row]
def valid_in_col(self, col, num):
return all(self.board[row][col] != num for row in range(9))
--fcc-editable-region--
def valid_in_square(self, row, col, num):
row_start = (row // 3) * 3
--fcc-editable-region--
puzzle = [
[0, 0, 2, 0, 0, 8, 0, 0, 0],
[0, 0, 0, 0, 0, 3, 7, 6, 2],
[4, 3, 0, 0, 0, 0, 8, 0, 0],
[0, 5, 0, 0, 3, 0, 0, 9, 0],
[0, 4, 0, 0, 0, 0, 0, 2, 6],
[0, 0, 0, 4, 6, 7, 0, 0, 0],
[0, 8, 6, 7, 0, 4, 0, 0, 0],
[0, 0, 0, 5, 1, 9, 0, 0, 8],
[1, 7, 0, 0, 0, 6, 0, 0, 5]
]
gameboard = Board(puzzle)