Fall 2004 Cs307 Midterm 1 Suggested Solution and Key

1.	The answer as below or -2. Note do not count off for differences in spacing, capitilization, or leading zeros.

A.	12

B.	2 4 4 3

C.	1

D.	0.0 0.5 1.0 1.5

E.	total54

F.	vessel weight: 2000

G.	Syntax error

H.	vessel weight: 2000
	vessel weight: 3000
	
I.	vessel weight: 1500
	vessel weight: 5000
	vessel weight: 1500
	
J.	vessel weight: 2000, number of masts: 2

K.	vessel weight: 1000, number of masts: 1

L.	vessel weight: 3500, number of masts: 2

M.	false
( 0 = -2, f = -1)

N.	Yes, a null pointer exception could occur if list = null or an array index out of bounds exception could occur if x < 0 or x >= list.length (Or words to that effect. If only one of the sources of a possible exception is mentioned full credit is still given.)

O.	7

2.	
public int longestStreak(int[] readings, int threshold)
{	int max = 0;
	int current = 0;
	for(int i = 0; i < readings.length; i++)
	{	if( readings[i] >= threshold )
		{	current++;
			if( current > max )
				max = current;
		}
		else
			current = 0;
	}
	return max;
}

3.	
public void eliminateTerm(int col)
{	boolean zeroFound = false;
	int row = 0;
	while( row < myCells.length && !zeroFound )
	{	zeroFound = myCells[row][col] == 0;
		row++;
	}
	if( !zeroFound )
	{	double factor;
		for(row = 1; row < myCells.length; row++)
		{	factor = -( myCells[row][col] / myCells[0][col] );
			for(int c = 0; c < myCells[0].length; c++)
				myCells[row][c] += myCells[0][col] * factor;
		}
	}
	return zeroFound;
}

4.

public class RadioStation
{
	private double dMyFreq;
	private String myCallLetters;
	private String myFormat;
	
	public RadioStation(doublee freq, String callLetters, String format)
	{	dMyFreq = freq;
		myCallLetters = callLetters;
		myFomat = format;
	}
	
	public void changeFormat(String newFormat)
	{	myFormat = format;
	}
	
	public String toString()
	{	return "frequency: " + dMyFreq + ", call letters: " + myCallLetters
			+ ", format: " + myFormat;
	}
	
	public boolean equals(Object other)
	{	RadioStation r = (RadioStation)other;
		return dMyFreq == r.dMyFreq && myCallLetters.equals( r.myCallLetters )
			&& myFormat.equals( r.myFormat );
	}
}

4 points for methods
4 points for instance variables
do not take off points for minor syntax errors such as semicolns or capitilization.
take off 1 point for each significant error in a method up to 4 per method.