package com.company;

/** * Created by Administrator on 2016/9/15. */public class EigthQueue {    private static int N = 8;    private int count = 0; // 总方案数    private int[] flag = {-1, -1, -1, -1, -1, -1, -1, -1};    //回溯法递归实现八皇后问题    //输出棋盘    private void printChessboard(){        int [][]chessboard = new int[N][N];        for ( int i=0; i<N; i++) {            chessboard[i][flag[i]] = 1;        }        for ( int i=0; i<N; i++) {            for ( int j=0; j<N; j++) {                System.out.print(String.format("%d ", chessboard[i][j]));            }            System.out.println();        }    }    private boolean checkQueen(int p){        boolean flag_t = true;        int pv = flag[p];        if ( p==0) {            return flag_t;        }        p--;        for ( int i=1; p>=0; p--, i++) {            if ( flag[p]==pv || flag[p]==pv-i || flag[p]==pv+i) {                flag_t = false;            }        }        return flag_t;    }    public void eightQueen(int p){        for ( int i=0; i<N; i++) {            flag[p] = i;            if ( checkQueen( p)==true && p==7) {                count++;                System.out.println("第" + count + "种:");                printChessboard( );            }            else if ( checkQueen( p ) == true){                eightQueen(p+1);            }        }    }

    public static void main(String[]args){        // 记录开始时间        long a=System.currentTimeMillis();        EigthQueue eigthQueue = new EigthQueue();        eigthQueue.eightQueen(0);        // 记录结束时间        System.out.println("\r<br>执行耗时 : "+(System.currentTimeMillis()-a)/1000f+" 秒 ");    }}