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我正在编写一个程序，其中我有一块板（3 x 3 矩阵），我必须通过逻辑交换特定行和列中的值与其相邻的行和列，如果我在 [0,0 处有 0 值] 然后我想要两块板。一个板在 [0,1] 处具有 0 值，在 [0,0] 处具有 [0,1]s 值，在 [1,0] 处具有 0 值并且在 [0,0] 处具有 [1,0]s 值的另一块板， 0]。但是在实现以下代码后，我有两个具有相同值的板，我无法理解对这些错误值的任何解释。

编辑：下面我有两个相关的类和相关的方法。问题在于 Board 类的邻居方法。似乎当我在邻居方法中创建一个板时，它并没有做它应该做的事情。

板级

public final class Board {
private final int dimen;
private final int[][] blocks;

public Board(int[][] blocks)           // construct a board from an N-by-N array of blocks
    // (where blocks[i][j] = block in row i, column j)
{
    this.dimen = blocks.length;
    this.blocks = new int[dimen][dimen];
    for (int i = 0; i < dimen; ++i) {
        for (int j = 0; j < dimen; ++j) {
            this.blocks[i][j] = blocks[i][j];
            System.out.println (this.blocks[i][j]);
        }
    }
...
...

public Iterable<Board> neighbors()     // all neighboring boards
{
    Stack<Board> neighborStack = new Stack <Board>();
    int x = 0, y = 0;
    outer : for (int i = 0; i < dimen; ++i){
        for (int j = 0; j < dimen; ++j) {
            if (this.blocks[i][j] == 0) {
                x = i;
                y = j;
                break outer;        
            }
        }
    }

    if (x == 0)
    {
        if (y == 0) {
            int tmpBlocks1[][] = Arrays.copyOf (this.blocks, this.blocks.length );
            int tmpBlocks2[][] = Arrays.copyOf (this.blocks, this.blocks.length );

            tmpBlocks1[0][0] = tmpBlocks1[0][1];
            tmpBlocks1[0][1] = 0;

            tmpBlocks2[0][0] = tmpBlocks2[1][0];
            tmpBlocks2[1][0] = 0;

            Board tmpBoard1 = new Board (tmpBlocks1);
            neighborStack.push (tmpBoard1);

            Board tmpBoard2 = new Board (tmpBlocks2);               
            neighborStack.push (tmpBoard2);

}

求解器类：

public final class Solver {

private MinPQ <SearchNode> pqOriginal;
private MinPQ <SearchNode> pqTwin;
Stack <Board> shortestBoardSequence = null;
int moves = 0;

public Solver(Board initial)            // find a solution to the initial board (using the A* algorithm)
{
    pqOriginal = new MinPQ<SearchNode>();
    pqTwin = new MinPQ<SearchNode>();
    pqOriginal.insert(new SearchNode (moves, initial, null) );
    pqTwin.insert(new SearchNode (moves, initial.twin(), null) );
}

public boolean isSolvable()             // is the initial board solvable?
{
    SearchNode originalNode = null;
    SearchNode twinNode = null;
    Stack <Board> neighborBoards = null;
    while (!pqOriginal.isEmpty() || !pqTwin.isEmpty()) {

        originalNode = pqOriginal.delMin();
        // shortestBoardSequence.push(originalNode.board);

        neighborBoards = (Stack<Board>)originalNode.board.neighbors();
...
}
...
}
...
public static void main(String[] args)  // solve a slider puzzle (given below)
{
    // create initial board from file
    In in = new In(args[0]);
    int N = in.readInt();
    int[][] blocks = new int[N][N];
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
        blocks[i][j] = in.readInt();
    Board initial = new Board(blocks);

    // solve the puzzle
    Solver solver = new Solver(initial);

    // print solution to standard output
    if (!solver.isSolvable()) // SEE THE ISSOLVABLE
        StdOut.println("No solution possible");
    ..
 }
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1 回答 1

4

这可能是因为您有一个二维数组，而您只复制一维。

通过做：

int tmpBlocks1[][] = Arrays.copyOf (blocks, blocks.length );

您实际上只是在复制行引用，而不是行数据。你正在做相当于：

int[] row0 = {0,0,0};
int[] row1 = {0,0,0};
int[] row2 = {0,0,0};
int[][] blocks = {row0, row1, row2};
int[][] tmpBlocks1 = {row0, row1, row2};

因此与 .tmpBlocks拥有相同的行blocks。

您需要执行所谓deep copy的数组 a 。

演示问题的示例代码：

public final class Test<T> {
  int[][] blocks = {{0,1,2},{10,11,12},{20,21,22}};
  int[][] copyOfBlocks = Arrays.copyOf(blocks, blocks.length);
  int[][] deepCopyOfBlocks = {
    Arrays.copyOf(blocks[0], blocks[0].length),
    Arrays.copyOf(blocks[1], blocks[1].length),
    Arrays.copyOf(blocks[2], blocks[2].length)
  };

  public void test() {
    System.out.println("Before");
    System.out.println("Blocks: "+Arrays.deepToString(blocks));
    System.out.println("Shallow Copy: "+Arrays.deepToString(copyOfBlocks));
    System.out.println("Deep Copy: "+Arrays.deepToString(deepCopyOfBlocks));

    // Change blocks and copy and deep copy.
    blocks[0][0] = 99;
    copyOfBlocks[0][0] = 88;
    deepCopyOfBlocks[0][0] = 77;

    System.out.println("After");
    System.out.println("Blocks: "+Arrays.deepToString(blocks));
    System.out.println("Shallow Copy: "+Arrays.deepToString(copyOfBlocks));
    System.out.println("Deep Copy: "+Arrays.deepToString(deepCopyOfBlocks));
  }

  public static void main(String[] args) throws InterruptedException {
    try {
      Test test = new Test();
      test.test();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

印刷：

Before
Blocks: [[0, 1, 2], [10, 11, 12], [20, 21, 22]]
Shallow Copy: [[0, 1, 2], [10, 11, 12], [20, 21, 22]]
Deep Copy: [[0, 1, 2], [10, 11, 12], [20, 21, 22]]
After
Blocks: [[88, 1, 2], [10, 11, 12], [20, 21, 22]]
Shallow Copy: [[88, 1, 2], [10, 11, 12], [20, 21, 22]]
Deep Copy: [[77, 1, 2], [10, 11, 12], [20, 21, 22]]

请注意，对 99 的更改被对 88 的更改覆盖，这表明副本是指原始的行。使用 77 时只有深拷贝受到影响。

于 2012-09-26T13:04:44.397 回答