Checks if queen is under attack

        :param col: Column number
        :param queens: list of queens
        :return: True iff queen is under attack

def under_attack(col, queens):
        """Checks if queen is under attack

        :param col: Column number
        :param queens: list of queens
        :return: True iff queen is under attack
        """
        left = right = col
        for _, column in reversed(queens):
            left, right = left - 1, right + 1
            if column in (left, col, right):
                return True
        return False