我试图制作一个程序来解决八皇后问题，但每次运行代码时我都会遇到异常错误，这就是我所拥有的。我对该怎么做有点困惑。对方向的任何帮助将不胜感激。
线程“main”中的异常 java.lang.ArrayIndexOutOfBoundsException:-1 at Queens.isUnderAttack(Queens.java:132) at Queens.placeQueens(Queens.java:78) at Queens.main(Queens.java:155)
public class Queens
{
//squares per row or column
public static final int BOARD_SIZE = 8;
//used to indicate an empty square
public static final int EMPTY = 0;
//used to indicate square contains a queen
public static final int QUEEN = 1;
private int board[][]; //chess board
public Queens()
{
//constructor: Creates an empty square board.
board = new int[BOARD_SIZE][BOARD_SIZE];
}
//clears the board
//Precondition: None
//Postcondition: Sets all squares to EMPTY
public void clearBoard()
{
//loops through the rows
for(int row = 0; row < BOARD_SIZE; row++)
{
//loops through the columns
for (int column = 0; column < BOARD_SIZE; column++)
{
board[row][column] = EMPTY;
}
}
}
//Displays the board
//precondition: None
//postcondition: Board is written to standard output;
//zero is an EMPTY square, one is a square containing a queen (QUEEN).
public void displayBoard()
{
for (int row = 0; row < BOARD_SIZE; row++)
{
System.out.println("");
for (int column = 0; column < BOARD_SIZE; column++)
{
System.out.print(board[row][column] + " ");
}
}
}
//Places queens in columns of the board beginning at the column specified.
//Precondition: Queens are placed correctly in columns 1 through column-1.
//Postcondition: If a solution is found, each column of the board contains one queen and
//method returns true; otherwise, returns false (no solution exists for a queen anywhere in column specified).
public boolean placeQueens(int column)
{
if(column >= BOARD_SIZE)
{
return true; //base case
}
else
{
boolean queenPlaced = false;
int row = 1; // number of square in column
while( !queenPlaced && (row < BOARD_SIZE))
{
//if square can be attacked
**if (!isUnderAttack(row, column))**
{
setQueen(row, column); //consider next square in column
queenPlaced = placeQueens(column+1);
//if no queen is possible in next column,
if(!queenPlaced)
{
//backtrack: remover queen placed earlier
//and try next square in column
removeQueen(row, column);
//++row;
}
}
row++;
}
return queenPlaced;
}
}
//Sets a queen at square indicated by row and column
//Precondition: None
//Postcondition: Sets the square on the board in a given row and column to Queen.
private void setQueen(int row, int column)
{
board[row][column] = QUEEN;
}
//removes a queen at square indicated by row and column
//Precondition: None
//Postcondition: Sets the square on the board in a given row and column to EMPTY.
private void removeQueen(int row, int column)
{
board[row][column] = EMPTY;
}
//Determines whether the square on the board at a given row and column is
//under attack by any queens in the columns 1 through column-1.
//Precondition: Each column between 1 and column-1 has a queen paced in a square at
//a specific row. None of these queens can be attacked by any other queen.
//Postcondition: If the designated square is under attack, returns true: otherwise return false.
private boolean isUnderAttack(int row, int column)
{
for (int y=0; y<BOARD_SIZE; y++)
{
if (board[row][y] == QUEEN || // possible horizontal attack
board[row-column+y][y] == QUEEN || // diagonal NW
**board[row+column-y][y] == QUEEN) // diagonal SW**
return true;
}
return false;
}
private int index(int number)
{
//Returns the array index that corresponds to a row or column number.
//Precondition: 1 <= number <= BOARD_SIZE.
//Postcondition: Returns adjusted index value
return number -1 ;
}
//main to test program
public static void main(String[] args)
{
Queens Q = new Queens();
**if(Q.placeQueens(0))**
{
System.out.println(Q);
}
else
{
System.out.println("Not Possible");
}
}
}