LeetCode 36 - Valid Sudoku - 2023.10.03 solution

class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        """ Solution: Use three dicts-to-sets to track the three ways that repetition
        is not allowed.
        """
        rows_to_seen = dict()
        cols_to_seen = dict()
        squares_to_seen = dict()

        for c in range(9):
            if c not in cols_to_seen:
                cols_to_seen[c] = set()
            for r in range(9):
                if r not in rows_to_seen:
                    rows_to_seen[r] = set()
                if (c//3, r//3) not in squares_to_seen:
                    squares_to_seen[(c//3, r//3)] = set()
                current_value = board[c][r]
                if current_value == '.':
                    continue
                else:
                    current_value = int(current_value)
                if current_value == 5:
                    print(cols_to_seen[c])
                if current_value in cols_to_seen[c]:
                    return False
                if current_value in rows_to_seen[r]:
                    return False
                if current_value in squares_to_seen[(c//3, r//3)]:
                    return False
                cols_to_seen[c].add(current_value)
                rows_to_seen[r].add(current_value)
                squares_to_seen[(c//3, r//3)].add(current_value)
        return True