N_Queen problem

import java.util.Scanner;

public class nqueens {
	public static void main(String[] args) {
		Scanner scn=new Scanner(System.in);
		int n=scn.nextInt();
        System.out.println(Nqueens(new boolean[n][n], 0, ""));
        output(new boolean[n][n], 0, "");
	}
public static int Nqueens(boolean[][] board, int row, String ans) {
	int count=0;
	if(row==board.length) {
		
		return 1;
	}
	for(int col=0; col<board[0].length; col++) {
		if(isItSafe(board, row, col)) {
		board[row][col]=true;
		
		count+=Nqueens(board, row+1, ans+ "{"+row+"-"+col+"} ");
		}
	
		board[row][col]=false;
	}
	return count;
	}
public static void output(boolean[][] board, int row, String ans) {
	if(row==board.length) {
		System.out.print(ans+" ");
		return ;
	}
	for(int col=0; col<board[0].length; col++) {
		if(isItSafe(board, row, col)) {
		board[row][col]=true;
		output(board, row+1, ans+ "{"+(row+1)+"-"+(col+1)+"} ");
		}
	
		board[row][col]=false;
	}
	}
	public static boolean isItSafe(boolean[][] board, int row, int col) {
		int r=row-1;
		int c=col;
		while(r>=0) {
			if(board[r][c]) {
				return false;
			}
			r--;
		}
		r=row-1;
		c=col-1;
		while(r>=0 && c>=0) {
			if(board[r][c]) {
				return false;
			}
			r--;
			c--;
		}
		r=row-1;
		c=col+1;
		while(r>=0 && c<board[0].length) {
			if(board[r][c]) {
				return false;
			}
			r--;
			c++;
		}
		return true;
	}
	
}