蓝桥杯-2n皇后问题（注：提交到ACM的有关问题）

import java.util.Scanner;

/*输入的第一行为一个整数n，表示棋盘的大小。
接下来n行，每行n个0或1的整数，如果一个整数为1，
表示对应的位置可以放皇后，如果一个整数为0，表示对应的位置不可以放皇后。*/

public class Main {
   

    @SuppressWarnings("unused")
    private static int step = 0 ;

   

    //初始化数组
    @SuppressWarnings("resource")
    private static void setArrays(int[][]a){
        Scanner sc = new Scanner(System.in) ;
      

        for(int i =0 ;i < a.length ;++i){
            for(int j =0 ; j < a.length;++j){
                a[i][j] = sc.nextInt() ;
            }
        }
    }
   

    //打印数组
    @SuppressWarnings("unused")
    private static void printArrays(int[][]a){
      

        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a.length; j++) {
                System.out.print(a[i][j]+" ");
            }
            System.out.println();
        }
    }
   

    //判断i,j 位置是否合法
    @SuppressWarnings("unused")
    private static boolean legalWhiteQueen(int[][]a,final int i ,final int j) {
        for(int n = 0 ;n < i ; ++n){
            for(int m = 0 ; m < a.length ; ++m){
                if(a[n][m] == 2){
                    if(Math.abs(i-n) == Math.abs(j- m) || j == m) return false;
                }else continue ;

            }
        }
        return true;
    }
   

    //判断i，j位置是否合法
    @SuppressWarnings("unused")
    private static boolean legalBlackQueen(int[][]a,final int i ,final int j) {
      

        for(int n = 0 ; n < i ; n++){
           

            for(int m = 0 ; m < a.length ;++m){
                if(a[n][m] == 3){
                    if(Math.abs(i-n) == Math.abs(j-m) || j == m)return false;
                }
            }
        }
      

        return true;
    }
   

    //TODO 其次判断黑皇后
    private static void blackQueen(int[][]a,int tag){
        if(tag == a.length){step++;/*System.out.println("step:" +step);printArrays(a);System.out.println();*/}
        else{
            for(int j = 0 ; j < a.length ; ++j){
                if(a[tag][j] != 2 && a[tag][j] != 0 ){
                    a[tag][j] = 3;
                    if(legalBlackQueen(a, tag, j)){
                        blackQueen(a, tag+1);
                    }
                    a[tag][j] = 1;
                }
            }
        }
    }
   

    // TODO 首先判断白皇后
    @SuppressWarnings("unused")
    private static void whiteQueen(int[][]a,int tag){
        if(tag == a.length)blackQueen(a, 0);
        else{
            for(int j = 0 ; j < a.length ; ++j){
                if(a[tag][j] != 0){
                    a[tag][j] = 2;
                    if(legalWhiteQueen(a, tag, j)){
                        whiteQueen(a, tag+1);
                    }
                    a[tag][j] = 1;
                }
            }
           

        }
      

      

    }
   

    @SuppressWarnings({ "unused", "resource" })
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

            int n = sc.nextInt() ;
            int[][]a = new int[n][n] ;
           

            setArrays(a);
   

            whiteQueen(a, 0);
            System.out.println(step);
           

      

    }
}