java - 八皇后数组越界 (Java)

Question

我正在尝试制作一个程序，通过递归执行八皇后，但我不断收到数组越界错误。我已经遇到这个问题有一段时间了，但我似乎无法真正找出问题所在。这是我的代码:

public class Queens {

 public int currColumn = 0;
 public static final int BOARD_SIZE = 8;
 public static final int EMPTY = 0;
 public static final int QUEEN = 1;
 private int board[][];

 public Queens() {
  board = new int[BOARD_SIZE][BOARD_SIZE];
 }

 public void clearBoard() {
  for (int x = 0; x <= BOARD_SIZE; x++) {
   for (int y = 0; y <= BOARD_SIZE; y++) {
    board[x][y] = 0;
   }

  }
 }

 public void displayBoard() {
  for (int x = 0; x < BOARD_SIZE; x++) {
   System.out.print("\n");
   for (int y = 0; y < BOARD_SIZE; y++) {
    System.out.print(board[x][y]);
   }

  }
 }

 public boolean placeQueens(int column) {
  if (column > BOARD_SIZE) {
   return true;
  } else {
   boolean queenPlaced = false;
   int row = 1;

   while (!queenPlaced && (row <= BOARD_SIZE)) {
    if (isUnderAttack(row, column)) {
     ++row;
    } else {
     setQueen(row, column);
     queenPlaced = placeQueens(column + 1);

     if (!queenPlaced) {
      removeQueen(row, column);
      ++row;
     }

    }
   }

   return queenPlaced;
  }
 }

 public void setQueen(int row, int column) //SET BACK TO PRIVATE
  {
   board[row][column] = 1;
  }

 private void removeQueen(int row, int column) {
  board[row][column] = 0;
 }

 private boolean isUnderAttack(int row, int column) {
  if (column == 0) {
   return false;
  }

  int prevColumn = column - 1;
  int prevRow = index(prevColumn);

  while (prevColumn >= 0) {
   prevRow = index(prevColumn);

   for (int i = 0; i > BOARD_SIZE; i++) {
    if (prevRow == row && prevColumn + i == column) //Going right
    {
     return true;
    }

    if (prevRow + i == row && prevColumn + i == column) //Going up/right
    {
     return true;
    }


    if (prevRow - i == row && prevColumn + i == column) //Going down/right
    {
     return true;
    }
   }


   prevColumn--;
  }

  return false;

 }

 public int index(int column) //BACK TO PRIVATE
  {

   for (int i = 0; i < 8; i++) {
    if (board[i][column] == 1) {
     return i;
    }
   }

   return 0;


  }

 public static void main(String[] args) {
  Queens x = new Queens();

  if (x.placeQueens(1) == true) {
   x.displayBoard();
  } else {
   System.out.println("No solution found");
  }
 }
}

Answer 1

第一个问题:

public void clearBoard()
{
    for(int x = 0; x < BOARD_SIZE; x++) // changed from x <= BOARD_SIZE
    {
        for(int y = 0; y < BOARD_SIZE; y++) // changed from y <= BOARD_SIZE
        {
            board[x][y] = 0;
        }

    }
}

数组索引计数从0开始到size-1。 board[8][8] 中没有任何内容。

另一个问题

/* ... */
while(prevColumn >= 0)
    {
        prevRow = index(prevColumn);

        for(int i = 0; i > BOARD_SIZE; i++) // i=0; i> BOARD_SIZE is always false, so no looping mechanism
        { /* ... */ }

更改为

 for(int i = 0; i < BOARD_SIZE; i++) // corrected

另一个问题？

if(column > BOARD_SIZE) when `column = 8`

成功

if(column >= BOARD_SIZE)

另一个问题:

  while(!queenPlaced && (row <= BOARD_SIZE))

成功

 row < BOARD_SIZE

还有另一个吗？

queenPlaced = placeQueens(column + 1); // What if column = 7