八皇后

public class EightQueenDemo {
    
    public static int count = 0;
    public boolean check(int array[][], int num, int i, int j) {
        for(int k = 0; k < num; k++) {
            if(array[i][k] == 1)
                return false;
            if(array[k][j] == 1)
                return false;
        }
        for(int s = i - 1, t = j - 1; s >= 0 && t >= 0; s--, t--) {
            if(array[s][t] == 1)
                return false;
        }
        for(int s = i - 1, t = j + 1; s >= 0 && t < num; s--, t++) {
            if(array[s][t] == 1)
                return false;
        }
        return true;
    }
    
    private void printQueen(int[][] array, int num) {
        System.out.println(num + "皇后的一种解法：");
        for(int i = 0; i < num; i++) {
            for(int j = 0; j < num; j++) {
                System.out.print(array[i][j] + " ");
            }
            System.out.println();
        }
    }
    
    public void find(int[][] array, int num, int row) {
        if(row > 7) {
            count++;
            printQueen(array, num);
            return;
        }
        for(int col = 0; col < num; col++) {
            if(check(array, num, row, col)) {
                array[row][col] = 1;
                find(array, num, row + 1);
                array[row][col] = 0;//一种解法找完后，将本位置重新置为0
            }
        }
    }
    
    public static void main(String[] args) {
        int num = 8;
        int[][] array = new int[num][num];
        EightQueenDemo eqd = new EightQueenDemo();
        eqd.find(array, num, 0);
        System.out.println("八皇后一共有:" + count + "种解法");
    }
}