APCS Written Test Practice 2013

APCS-Test-Practice-2013.java

// 1a
public DownloadInfo getDownloadInfo(String title) {
	for(DownloadInfo elem : downloadList) {
		if(elem.getTitle().equals(title)) {
			return elem;
		}
	}
	return null;
}

// 1b
public void updateDownloads(List<String> titles) {
	for(String title : titles) {
		if(getDownloadInfo(title) != null) {
			getDownloadInfo(title).incrementTimesDownloaded();
		} else {
			downloadList.add(new DownloadInfo(title));
		}
	}
}

// 2a
public TokenPass(int playerCount) {
	board = new int[playerCount];
	for(int i = 0; i < board.length; i++) {
		board[i] = (int)((Math.random() * 10) + 1));
	}
	currentPlayer = (int)(Math.random() * playerCount);
}

// 2b
public void distributeCurrentPlayerTokens() {
	int tokens = board[currentPlayer];
	board[currentPlayer] = 0;
	for(int i = 1; i <= tokens; i++) {
		board[(currentPlayer + i) % board.length] += 1;
	}
}

// 3a
// skipped because we didn't do GridWorld

// 3b
// skipped because we didn't do GridWorld

// 4a
public SkyView(int numRows, int numCols, double[] scanned) {
	view = new double[numRows][numCols];
	int curIndex = 0; // current index in scanned
	
	for(int curRow = 0; curRow < numRows; curRow++) {
		if(curRow % 2 == 0) { // even row, going up
			for(int curCol = 0; curCol < numCols; curCol++) {
				view[curRow][curCol] = scanned[curIndex];
				curIndex++;
			}
		} else { // odd row, going down
			for(int curCol = numCols - 1; curCol >= 0; curCol--) {
				view[curRow][curCol] = scanned[curIndex];
				curIndex++;
			}
		}
	}
}

// 4b
public double getAverage(int startRow, int endRow, int startCol, int endCol) {
	double sum = 0;
	int numValues = 0; // the number of values added to sum, used to calculate average
	for(int curRow = startRow; curRow <= endRow; curRow++) {
		for(int curCol = startCol; curCol <= endCol; curCol++) {
			sum += view[curRow][curCol];
			numValues++;
		}
	}
	return (sum / numValues);
}