Method placeQueens

java/Chapter 9/Question9_9/Question.java:35–46

(int row, Integer[] columns, ArrayList<Integer[]> results)

	}
	
	public static void placeQueens(int row, Integer[] columns, ArrayList<Integer[]> results) {
		if (row == GRID_SIZE) { // Found valid placement
			results.add(columns.clone()); 
		} else {
			for (int col = 0; col < GRID_SIZE; col++) {			
				if (checkValid(columns, row, col)) {
					columns[row] = col;	// Place queen
					placeQueens(row + 1, columns, results);	
				}		
			}
		}
	}
	
	public static void clear(Integer[] columns) {
		for (int i = 0; i < GRID_SIZE; i++) {