我在这里看到的帖子与此类似，但我的情况略有不同。
我编写了displayBoard方法，但最后一列没有返回Queen。
是因为女王的值为1并且丢掉数字吗？
它一直告诉我，我有ArrayOutOfBoundsException: -1
我知道数组计数为0但我仍然无法使其工作
public class Queens
{
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()
{
board = new int[BOARD_SIZE][BOARD_SIZE];
}
public void displayBoard () {
int counter = 0;
for (int i = 0; i < BOARD_SIZE; i++)
{
for (int j = 0 ; j < BOARD_SIZE; j++)
{
if (board[i][j] == QUEEN )
{
System.out.print("| X |");
counter++;
}
else
{
System.out.print("| 0 |");
}
}
System.out.println();
}
}
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)) {
++row; // consider next square in column
} // end if
else { // place queen and consider next column
setQueen(row, column);
queenPlaced = placeQueens(column+1);
// if no queen is possible in the next column,
if (!queenPlaced) {
// backtrack: remove queen placed earliers
// and try next square in column
removeQueen(row, column);
++row;
} // end if
} // end if
} // end while
return queenPlaced;
} // end if
} // end placeQueens
private void setQueen(int row, int column) {
board[row-1][column-1] = QUEEN;
} // end setQueen
private void removeQueen(int row, int column) {
board[row-1][column-1] = EMPTY;
} // end setQueen
private boolean isUnderAttack(int row, int column) {
// check column
for (int i=0; i<row-1; i++){
if (board[i][column-1]==1){
return true;
}
}
// check row
for (int i=0; i<column-1; i++) {
if (board[row-1][i] == 1){
return true;
}
}
// check lower diagnal
int lower_dir_row = row-2;
int lower_dir_column = column-2;
while (lower_dir_row>=0 && lower_dir_column>=0){
if (board[lower_dir_row][lower_dir_column]==1){
return true;
} else {
lower_dir_row = lower_dir_row -1;
lower_dir_column = lower_dir_column -1;
}
}
// check upper diagnal
int upper_dir_row = row;
int upper_dir_column = column-2;
while (upper_dir_row<BOARD_SIZE && upper_dir_column>=0){
if(board[upper_dir_row][upper_dir_column] ==1){
return true;
}else{
upper_dir_row = upper_dir_row +1;
upper_dir_column = upper_dir_column -1;
}
}
return false;
} // end isUnderAttack
public static void main(String[] s)
{
Queens q = new Queens();
q.placeQueens(0);
q.displayBoard();
}
} // end Queens
答案 0 :(得分：2)
您需要在placeQueens（）方法中更改while循环
while ( !queenPlaced && (row <= BOARD_SIZE) ) {...}
while循环应该是＆lt;确保您永远不会尝试以索引BOARD_SIZE访问您的电路板。一旦行== BOARD_SIZE，您将尝试访问该板，这将使您看到的索引超出范围异常。将其更改为以下
while ( !queenPlaced && (row < BOARD_SIZE) ) {...}
此外，在您的setQueen（...）和removeQueen（...）函数中，您永远不会进行边界检查，并假设您可以使用传入的参数访问该板。在设置或移除电路板阵列中的后置元件之前，您需要确保两个值都小于BOARD_SIZE。
private void setQueen(int row, int column) {
if(row - 1 < BOARD_SIZE && column - 1 < BOARD_SIZE)
board[row-1][column-1] = QUEEN;
} // end setQueen
private void removeQueen(int row, int column) {
if(row - 1 < BOARD_SIZE && column - 1 < BOARD_SIZE)
board[row-1][column-1] = EMPTY;
} // end setQueen
最后，既然您正在申请自己的1个，那么您应该将主要电话改为（Credit @Ian Mc）
q.placeQueens(1);
但是，如果您想简化程序，则不应该应用偏移量，因为这通常会引入用户错误。 以下是您应该如何使您的程序无偏移
（1）在isUnderAttack方法中添加检查，以确保在使用仅检查0和更大值的简单检查访问它们之前查看电路板中的有效行和列
private boolean isUnderAttack(int row, int column) {
// check column
for (int i=0; i<row-1; i++){
/* add a check to ensure the column offset index is valid */
if (column - 1 >= 0 && board[i][column-1]==1){
return true;
}
}
// check row
for (int i=0; i<column-1; i++) {
/* add a check to ensure the row offset index is valid */
if (row - 1 >= 0 && board[row-1][i] == 1){
return true;
}
}
（2）然后从删除和设置后置方法
中删除偏移量private void setQueen(int row, int column) {
if(row < BOARD_SIZE && column < BOARD_SIZE)
board[row][column] = QUEEN;
} // end setQueen
private void removeQueen(int row, int column) {
if(row < BOARD_SIZE && column < BOARD_SIZE)
board[row][column] = EMPTY;
} // end setQueen
（3）确保在placeQueens（...）方法中从0循环到BOARD_SIZE - 1
while ( !queenPlaced && (row < BOARD_SIZE) ) {
（4）最后从索引0开始
q.placeQueens(0);
输出
| 0 || 0 || 0 || 0 || 0 || 0 || 0 || 0 |
| 0 || 0 || 0 || 0 || 0 || 0 || X || X |
| 0 || 0 || 0 || 0 || 0 || X || 0 || 0 |
| 0 || 0 || 0 || 0 || X || 0 || 0 || 0 |
| 0 || 0 || 0 || X || 0 || 0 || 0 || 0 |
| 0 || 0 || X || 0 || 0 || 0 || 0 || 0 |
| 0 || X || 0 || 0 || 0 || 0 || 0 || 0 |
| X || 0 || 0 || 0 || 0 || 0 || 0 || 0 |
答案 1 :(得分：1)
q.placeQueens(0); // here is the Error
因为你要设置女王
int row = 1;
.
.
.
setQueen(row, column); // The program will enter with row 1 and column 0
并且
private void setQueen(int row, int column) {
board[row-1][column-1] = QUEEN; // Here comes with row=1 and column 0
}
使用
进行测试q.placeQueens(1);
正在显示
| X || 0 || 0 || 0 || 0 || 0 || 0 || 0 |
| 0 || 0 || 0 || 0 || X || 0 || 0 || 0 |
| 0 || X || 0 || 0 || 0 || 0 || 0 || 0 |
| 0 || 0 || 0 || 0 || 0 || X || 0 || 0 |
| 0 || 0 || X || 0 || 0 || 0 || 0 || 0 |
| 0 || 0 || 0 || 0 || 0 || 0 || X || 0 |
| 0 || 0 || 0 || X || 0 || 0 || 0 || 0 |
| 0 || 0 || 0 || 0 || 0 || 0 || 0 || 0 |