#
# ps9pr1.py (Problem Set 9, Problem 1)
#
# A Connect Four Board class
#
# Computer Science 111
#

class Board:
    """ a data type for a Connect Four board with arbitrary dimensions
    """   
    ### add your constructor here ###


    def __repr__(self):
        """ Returns a string that represents a Board object.
        """
        s = ''         #  begin with an empty string

        # add one row of slots at a time to s
        for row in range(self.height):
            s += '|'   # one vertical bar at the start of the row

            for col in range(self.width):
                s += self.slots[row][col] + '|'

            s += '\n'  # newline at the end of the row

        ### add your code here ###
        
        return s

    def add_checker(self, checker, col):
        """ adds the specified checker (either 'X' or 'O') to the
            column with the specified index col in the called Board.
            inputs: checker is either 'X' or 'O'
                    col is a valid column index
        """
        assert(checker == 'X' or checker == 'O')
        assert(col >= 0 and col < self.width)
        
        ### put the rest of the method here ###
        

    
    ### add your reset method here ###
    
    def add_checkers(self, colnums):
        """ takes a string of column numbers and places alternating
            checkers in those columns of the called Board object,
            starting with 'X'.
            input: colnums is a string of valid column numbers
        """
        checker = 'X'   # start by playing 'X'

        for col_str in colnums:
            col = int(col_str)
            if 0 <= col < self.width:
                self.add_checker(checker, col)

            if checker == 'X':
                checker = 'O'
            else:
                checker = 'X'

    ### add your remaining methods here