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照著做

Problem

Tic-tac-toe is played by two players A and B on a 3 x 3 grid.

Here are the rules of Tic-Tac-Toe:

  • Players take turns placing characters into empty squares ( ).
  • The first player A always places X characters, while the second player B always places O characters.
  • X and O characters are always placed into empty squares, never on filled ones.
  • The game ends when there are 3 of the same (non-empty) character filling any row, column, or diagonal.
  • The game also ends if all squares are non-empty.
  • No more moves can be played if the game is over.

Given an array moves where each element is another array of size 2 corresponding to the row and column of the grid where they mark their respective character in the order in which A and B play.

Return the winner of the game if it exists (A or B), in case the game ends in a draw return Draw, if there are still movements to play return Pending.

You can assume that moves is valid (It follows the rules of Tic-Tac-Toe), the grid is initially empty and A will play first.

 

Example 1:

Input: moves = [[0,0],[2,0],[1,1],[2,1],[2,2]]Output: AExplanation: A wins, he always plays first.X      X      X      X      X      ->     ->  X  ->  X  ->  X        O      O      OO     OOX

Example 2:

Input: moves = [[0,0],[1,1],[0,1],[0,2],[1,0],[2,0]]Output: BExplanation: B wins.X      X      XX     XXO    XXO    XXO    ->  O  ->  O  ->  O  -> XO  -> XO                                     O

Example 3:

Input: moves = [[0,0],[1,1],[2,0],[1,0],[1,2],[2,1],[0,1],[0,2],[2,2]]Output: DrawExplanation: The game ends in a draw since there are no moves to make.XXOOOXXOX

Example 4:

Input: moves = [[0,0],[1,1]]Output: PendingExplanation: The game has not finished yet.X   O

 

Constraints:

  • 1 <= moves.length <= 9
  • moves[i].length == 2
  • 0 <= moves[i][j] <= 2
  • There are no repeated elements on moves.
  • moves follow the rules of tic tac toe.

Sol

class Solution:
    def tictactoe(self, moves: List[List[int]]) -> str:
        def win(c):
            for who in ["A", "B"]:
                if c[who] == 3:
                    return who
            return None
        tbl = [[None for _ in range(3)] for _ in range(3)]
        
        who = True
        for (i,j) in moves:
            tbl[i][j] = "A" if who else "B"
            who = not who
        
        rows = [Counter(r) for r in tbl]
        cols = [Counter([tbl[i][j] for i in range(3)]) for j in range(3)]
        cross = [Counter([tbl[0][0], tbl[1][1], tbl[2][2]]), Counter([tbl[2][0], tbl[1][1], tbl[0][2]])]
        ret = list(filter(lambda x: win(x) is not None, rows+cols+cross))
        if ret:
            return list(ret[0].keys())[0]
        elif len(moves) == 9:
            return "Draw"
        else:
            return "Pending"