public class Solution {
    private int res=0;
    public int totalNQueens(int n) {

        int[][] board = new int[n][n];
        helper(board,0);

        return res;
    }
    public void helper(int[][] board, int colIndex){

        if(colIndex==board.length){
            res++;
            return;
        }

        for(int i=0;i<board.length;i++){
            if(validate(board, i, colIndex)){
                board[i][colIndex] = 1;
                helper(board, colIndex+1);
                board[i][colIndex] = 0;
            }
        }
    }
    public boolean validate(int[][] board, int x, int y){

        for(int i=0;i<board.length;i++){
            for(int j=0;j<y;j++){
                if(board[i][j]==1 &&  (x + j == y + i || x + y == i + j || x == i)){
                    return false;
                }
            }
        }
        return true;
    }
}