private boolean validate(char[][] board, int x, int y) {
		for(int i = 0; i < board.length; i++) {
			for(int j = 0; j < y; j++) {
				/**
				 * x==i,same row
				 * x+y == i+j,/ diagonal
				 * x+j == y+i,\ diagonal
				 */
				if(board[i][j] == 'Q' && ( x + j == y + i || x + y == i + j || x == i ))
					return false;
			}
		}
		return true;
	}