public void solve(char[][] board) {
		if (board == null || board.length == 0 || board[0].length == 0) {
			return;
		}
		int length = board[0].length - 1;
		int height = board.length - 1;
		for (int i = 0; i < length; i++) {
			fill(board, 0, i);
			fill(board, height, length - i);
		}
		for (int j = 0; j < height; j++) {
			fill(board, j, length);
			fill(board, height - j, 0);
		}

		for (int i = 0; i <= height; i++) {
			for (int j = 0; j <= length; j++) {
				if (board[i][j] == 'O') {
					board[i][j] = 'X';
				} else if (board[i][j] == 'D') {
					board[i][j] = 'O';
				}
			}
		}
	}