eightqueue.java

这个是一个典型的用java编的八皇后的游戏

//用回朔搜索法解八皇后
import java.io.*;

public class EightQueue {
    String[][] rec = new String[8][8];

    int[] a = new int[8];

    int[] b = new int[15];

    int[] c = new int[15];

    int sum;

    public EightQueue() {
        super();
        for (int i = 0; i < this.rec.length; i++) {
            for (int j = 0; j < this.rec[i].length; j++) {
                this.rec[i][j] = "○";
            }
        }

    }

    public void prt() {
        System.out.println("");
        for (int i = 0; i < this.rec.length; i++) {
            for (int j = 0; j < this.rec[i].length; j++) {
                System.out.print(this.rec[i][j] + " ");
            }
            System.out.println("");
        }

       System.out.println("");
    }

    /**
     * set the queen of line i
     * 
     * @param i
     */
    void queue(int i) {
        for (int iColumn = 0; iColumn < 8; iColumn++) {
            if (a[iColumn] == 0 && b[i - iColumn + 7] == 0&& c[i + iColumn] == 0) {
                // do not conflict
                rec[i][iColumn] = "●";
                a[iColumn] = 1;
                b[i - iColumn + 7] = 1;
                c[i + iColumn] = 1;
                if (i < 7)
                    queue(i + 1);
                else {
                  
                    prt();
                    sum++;
                }
                // whatever how to put the queen, mission is impossible. rollback
                rec[i][iColumn] = "○";
                a[iColumn] = 0;
                b[i - iColumn + 7] = 0;
                c[i + iColumn] = 0;
            }
        }
    }

    /**
     * 8 queen
     * @param args
     */
    public static void main(String[] args) {
        EightQueue eq = new EightQueue();
        eq.queue(0);
        System.out.println(eq.sum);
    }
}