public class Queen {
    static final int QUEEN_MAX = 8;     // 皇后的数量 
    int[][] Queencount = new int[QUEEN_MAX][QUEEN_MAX];     // 分配8X8的数组，充当棋盘，存放皇后 
    int resultCount = 0;      // 记录皇后的放置方法的总数 
    int[] Queenplace = new int[QUEEN_MAX];    // 存放每行的皇后位置即第column行的皇后放置位置是Queenplace[column] 
    public void putQueen(int Rows) 
    { 
        int row = Rows;    // 行标 
        for (int column = 0; column < QUEEN_MAX; column++)    // column表示列标 
        { 
         if (Queencount[row][column] == 0)     // row行、column列可以放皇后 
            { 
                for (int rowi = row + 1; rowi < QUEEN_MAX; rowi++)     // for循环的作用是使其斜下方和正下方不为0 
                { 
                    Queencount[rowi][column]++; 
                    if (column - rowi + row >= 0) 
                    { 
                        Queencount[rowi][column - rowi + row]++;
                    } 
                    if (column + rowi - row < QUEEN_MAX) 
                    { 
                        Queencount[rowi][column + rowi - row]++; 
                    } 
                }
                Queenplace[row] = column;     // row行column列放了皇后 
                if (row == QUEEN_MAX - 1)     // 皇后已放满，打印出皇后布局 
                { 
                    printQueen(++resultCount); 
                } 
                else        // 否则继续排列下一行皇后 
                { 
                    putQueen(row + 1); 
                } 
                for (int rows = row + 1; rows < QUEEN_MAX; rows++)     // 回溯，在此行的皇后不放此列column 
                { 
                    Queencount[rows][column]--; 
                    if (column - rows + row >= 0) 
                    {
                        Queencount[rows][column - rows + row]--; 
                    } 
                    if (column + rows - row < QUEEN_MAX) 
                    { 
                        Queencount[rows][column + rows - row]--; 
                    } 
                } 
            } 
        } 
        if (row == 0) 
        { 
            System.out.println(QUEEN_MAX + "皇后问题共有" + resultCount + "个解."); 
        } 
    } 
    public void printQueen(int size)        // 打印皇后布局 
    { 
        System.out.println(QUEEN_MAX + "皇后的第" + size + "个解是:"); 
        System.out.println(); 
        for (int row = 0; row < QUEEN_MAX; row++) 
        { 
            for (int column = 0; column < QUEEN_MAX; column++) 
            { 
                System.out.print(Queenplace[row] == column ? " * " : " - "); 
            } 
            System.out.println(); 
        } 
        System.out.println(); 
    } 
    public static void main(String[] args) 
    { 
        Queen Q = new Queen(); 
        Q.putQueen(0); 
    } 
} 

八皇后问题