CS305J Fall 2006 final Exam suggested solutions and grading criteria.
1. Answer as written or -1. Missing "'s okay.

5
5
"2AT1" 
3.5
DC23
true
true


2. Answer as written or -2. [] or {} or () okay.

{}
{ 25 }
{7, 21}
{7, 3, 2, 5}


3. Suggested Solution:

public static boolean passed(double ave, boolean under){
	return (ave >= 70) || (under && ave >= 60);
}

criteria

1 point, header and parameters
3 points logic correct
1 point return


4. Suggested Solution

public static boolean alternateSigns(int[] data){
	if( data.length == 0 )
		return true;
	if( data[0] == 0 )
		return false;
	
	boolean positive = data[0] > 0;
	boolean good = true;
	int position = 1;
	while( good && position < data.length  - 1){
		if( positive )
			good = data[position + 1] < 0;
		else
			good = data[position + 1] > 0;
		position++;
		positive = !positive;
	}
	
	return good;
}

criteria:

1 point, special cases empty list and first element 0

3 points, attempt to traverse list
3 points, correctly traverse list

3 points, attempt to check alternating sign
4 points, correctly check alternating sign. (-2 if 0s not handled correctly)

1 point, return result
 

5. Suggested Solution

public static int columnWithMaxTrues(boolean[][] mat){
	int maxTrues = -1;
	int colWithMax = -1;
	int numTrues = 0;
	
	for(int c = 0; c < mat[0].length; c++){
		numTrues = 0;
		for(int r = 0; r < mat.length; r++){
			if( mat[r][c] )
				numTrues++;
		}
		if( numTrues > maxTrues ) {
			colWithMax = c;
			maxTrues = numTrues;
		}
	}
	
	return colWithMax;
}

criteria:


1 point, attempt to traverse columns
2 points, correctly traverse columns (columns must be outer loop to earn this or must use temp array)

1 point, attempt to traverse rows
2 points, correctly traverse rows (columns must be inner loop to earn this or must use temp array)

2 points, attempt to track trues per column
2 points, correctly track trues per column

2 points, attempt to check and update information for column with max trues
2 points, correctly check and update information for column with max trues

1 point, return value
 
6. Suggested Solution:

public class Longhorn implements Critter{

	private int direction;
	private int stepsThisLeg;
	private int stepsSoFar;
	
	public Longhorn(){
		if( Math.random() > 0.5 )
			direction = NORTH;
		else
			direction = SOUTH;
		stepsThisLeg = 1;
		stepsSoFar = 0;
	}
	
	public int fight(String opponent){
		int result;
		if( Math.random() > 0.5 )
			result = SCISSORS;
		else
			result = ROCK;
		return result;
	}
	
	public Color getColor(){
		return Color.ORANGE;
	}
	
	public String toString(){
		return "B";
	}
	
	public int getMove(CritterInfo info){
		if( stepsSoFar == stepsThisLeg){
			stepsSoFar = 0;
			stepsThisLeg++;
			if( Math.random() > 0.5 )
				direction = NORTH;
			else
				direction = SOUTH;
		}
		
		stepsSoFar++;
		return direction;
	}
}

criteria:

1 point, header. Lose this if does not include implements Critter
3 points, fields / instance variables (-2 if not private) (partial credit possible) 
2 points, constructor. (could get tricky if getMove correct) (partial credit possible) 
2 points, fight (partial credit possible) 
1 point, getColor
1 point, toString
5 points, getMove (partial credit possible) 
 
7. Suggested Solution:

public static boolean oneDifferent(String s1, String s2){
	
	// check if lengths different by 2 or more characters
	if( Math.abs( s1.length() - s2.length() ) > 1 )
		return false;
		
	int smallestLength = Math.min( s1.length(), s2.length() );
	
	// set initial value of number of differences. If lengths different by 1 start at 1
	// difference, otherwise start at 0 differences
	int numDiff;
	if( s1.length() != s2.length() )
		numDiff = 1;
	else
		numDiff = 0;
	
	// move through each character in the Strings, incrementing number of differences
	// if the characters are not equal.
	int position = 0;
	while( position < smallestLength && numDiff <= 1){
		if( s1.charAt(position) != s2.charAt(position) )
			numDiff++;
		position++;
	}
	
	
	return numDiff == 1;
}
criteria:
2 points, attempt to traverse both Strings
2 points, correctly traverse both Strings

2 points, attempt to track number of differences
3 points, correctly track number of differences (-1 if doesn't handle case of Strings with difference in lengths is greater than 2)

1 return result

8. Suggested Solution:

public static void moveToFront(ArrayList<String> list, int length){
	int positionForShort = 0;
	String temp;
	
	for(int i = 0; i < list.size(); i++) {
		if( list.get(i).length() <= length ){
			temp = list.remove( i );
			list.add(positionForShort, temp);
			positionForShort++;
		}
	}
	
}

criteria:
1 point, attempt to traverse elements of list
2 points, correctly traverse elements of list

1 point, attempt to identify elements with Strings of proper length
2 points, correctly identify elements with Strings of proper length

1 point, attempt to move elements to front
3 points, correctly move elements to front while maintaining relative order
 
9. Suggested Solution:

public static int[] reverseInRange(int[] data, int min, int max){
	int numInRange = 0;
	
	for(int i = 0 ; i < data.length; i++){
		if( data[i] >= min && data[i] <= max ){
			numInRange++;
		}
	}
	
	int[] result = new int[numInRange];
	int positionInResult = 0;
	
	for(int i = data.length - 1; i >= 0; i--){
		if( data[i] >= min && data[i] <= max ){
			result[positionInResult] = data[i];
			positionInResult++;
		}
	}
	
	return result;
}

criteria:

2 points, attempt to find number of values in range
3 points, correctly find number of values in range

2 points declare result of proper size

3 points, attempt to add elements from data in range to result
4 points, correctly add elements from data in range to result. (must correctly reverse order)

1 point, return result