第一次实验——八皇后问题

public class Queen1 {  
    private int[] column;  
    private int[] rTol;//右上至左下是否有皇后  
    private int[] lTor;//左上至右下是否有皇后  
    private int[] queen;//解答  
    private int num;//解答的编号  
      
    public Queen1() {  
        column = new int[8+1];  
        rTol = new int[2*8+1];  
        lTor = new int[2*8+1];  
        for(int i=1;i<=8;i++)   
            column[i] = 1;  
            for(int i=1;i<=2*8;i++)   
                rTol[i] = lTor[i] = 1;  
                queen = new int[8+1];  
          
    }  
      
    public void backTrack(int i) {  
        if(i>8) {  
            showAnswer();  
        } else {  
            for(int j=1;j<=8;j++) {  
                if(column[j] == 1 && rTol[i+j] ==1 && lTor[i-j+8] == 1) {  
                    queen[i] = j;//设定为占用  
                    column[j] = rTol[i+j] = lTor[i-j+8] = 0;  
                    backTrack(i+1);  
                    column[j] = rTol[i+j] = lTor[i-j+8] = 1;  
                }  
            }  
        }  
    }  
      
    protected void showAnswer() {  
        num ++;  
        System.out.println("\n解答" + num);  
        for(int y=1;y<=8;y++) {  
            for(int x = 1;x<=8;x++) {  
                if(queen[y] == x) {  
                    System.out.print(" Q");  
                }else {  
                    System.out.print(" X");  
                }  
            }  
            System.out.println();  
        }  
    }  
      
    public static void main(String [] args) {  
        Queen1 queen = new Queen1();  
        queen.backTrack(1);  
    }  
  
}