在java中克隆和编辑int [] [] - 无法更改int [] []

发布于 2024-12-12 07:30:57 字数 684 浏览 0 评论 0原文

这是我的代码：

  public Move makeMove(int[][] board)

（...更多代码...）

 int[][] nextMove = board.clone(); 
  nextMove[i][j] = 1;
  int nextMaxMove = maxMove( nextMove );        

  System.out.println( next max move: " + nextMaxMove + " " + maxMove( board )  );

int[][] 棋盘 是一个 8x8 棋盘，我尝试计算棋盘游戏中的最佳动作。

当我找到一系列同样好的动作时，我想检查对手给出了我可以做的不同动作的可能性。因此，我clone() board，编辑克隆nextMove[i][j] = 1并调用maxMove code> 新板上的功能。

println 用于调试，我对 maxMove( nextMove ); 和 maxMove( board ) 得到相同的结果，这是错误的..看起来像 nextMove 保持不变..

原文

This is my code:

  public Move makeMove(int[][] board)

(... more code ...)

 int[][] nextMove = board.clone(); 
  nextMove[i][j] = 1;
  int nextMaxMove = maxMove( nextMove );        

  System.out.println( next max move: " + nextMaxMove + " " + maxMove( board )  );

the int[][] board is a 8x8 board and I attempt to calculate the best move in a board game.

When I have found a list of equaly good moves I want to check what possibilities the opponent have given the different moves I can do. So I clone() the board, edit the clone nextMove[i][j] = 1 and call the maxMove function on the new board.

the println is for debugging, and I get the same result for maxMove( nextMove ); and maxMove( board ), this is wrong.. It seems like nextMove remain unchanged..

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因为看清所以看轻 2024-12-19 07:30:57

发生这种情况是因为您的数据结构是一个数组的数组 - 在幕后，它是一个引用数组。您的克隆是浅副本，因此克隆包含原始数组。
此示例代码演示了这一点。

    int[][] x = new int[][] { { 1,3 }, { 5,7 }  };
    int[][] copyOfX = x.clone( );
    copyOfX[1][1]=13;

    for ( int i = 0; i < 2; i++ )
    {
        System.out.println(x[i] + "/" + copyOfX[i]);
        for ( int j = 0; j < 2; j++ )
        {
            System.out.println(x[i][j] + "/" + copyOfX[i][j]);
        }
    }

解决方案是显式复制二维数组的内容，而不是使用 .clone()。

This happens because your data structure is an array of arrays - which, under the hood, is an array of references. Your clone is a shallow copy, so the clone contains the original arrays.
This sample code demonstrates it.

    int[][] x = new int[][] { { 1,3 }, { 5,7 }  };
    int[][] copyOfX = x.clone( );
    copyOfX[1][1]=13;

    for ( int i = 0; i < 2; i++ )
    {
        System.out.println(x[i] + "/" + copyOfX[i]);
        for ( int j = 0; j < 2; j++ )
        {
            System.out.println(x[i][j] + "/" + copyOfX[i][j]);
        }
    }

The solution is to explicitly copy the contents of your 2-dimensional array, rather than using .clone().

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