Data is #4 from the from the 2022 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap22-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – repopulate method

public void repopulate()
{
  for(int r = 0; r < grid.length; r++)
  {
    for(int c = 0; c < grid[0].length; c++)
    {
      int rand = (int) (Math.random() * MAX) + 1;
      while(rand % 10 != 0 || rand % 100 == 0)
        rand = (int) (Math.random() * MAX) + 1;
      
      grid[r][c] = rand;
    }
  }
}

Part (b) – countIncreasingCols method

public int countIncreasingCols()
{
  int increasingCols = 0;
  
  for(int c = 0; c < grid[0].length; c++)
  {
    boolean isIncreasing = true;
    
    for(int r = 1; r < grid.length; r++)
      if(grid[r-1][c] > grid[r][c])
        isIncreasing = false;
    
    if(isIncreasing)
      increasingCols++;
  }
  
  return increasingCols;
}

2022 AP CS Exam Free Response Solutions

• Game Free Response Solution
• Textbook Free Response Solution
• ReviewAnalysis Free Response Solution

ReviewAnalysis is #3 from the from the 2022 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap22-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – getAverageRating method

public double getAverageRating()
{
  int ratingSum = 0;
  
  for(Review rev : allReviews)
    ratingSum += rev.getRating();
  
  return ratingSum / (double) allReviews.length;
}

Part (b) – collectComments method

public ArrayList<String> collectComments()
{
  ArrayList<String> comments = new ArrayList<String>();
  
  for(int i = 0; i < allReviews.length; i++)
  {
    String com = allReviews[i].getComment();
    if(com.indexOf("!") >= 0)
    {
      String formatted = i + "-" + com;
      String lastChar = formatted.substring(formatted.length() - 1);
      if( ! lastChar.equals("!") && ! lastChar.equals("."))
        formatted += ".";
      
      comments.add(formatted);
    }
  }
  
  return comments;
}

2022 AP CS Exam Free Response Solutions

• Game Free Response Solution
• Textbook Free Response Solution
• Data Free Response Solution

Textbook is #2 from the from the 2022 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap22-frq-computer-science-a.pdf?course=ap-computer-science-a

Textbook class

public class Textbook extends Book
{
  private int edition;

  public Textbook(String bookTitle, double bookPrice, int edition)
  {
    super(bookTitle, bookPrice);
    this.edition = edition;
  }

  public int getEdition()
  {
    return edition;
  }

  public String getBookInfo()
  {
    return super.getBookInfo() + "-" + edition;
  }

  public boolean canSubstituteFor(Textbook otherTextbook)
  {
    return this.getTitle().equals(otherTextbook.getTitle()) &&
        this.getEdition() >= otherTextbook.getEdition();
  }
}

2022 AP CS Exam Free Response Solutions

• Game Free Response Solution
• ReviewAnalysis Free Response Solution
• Data Free Response Solution

Game is #1 from the from the 2022 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap22-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – getScore method

public int getScore()
{
  int score = 0;
  
  if(levelOne.goalReached())
  {
    score += levelOne.getPoints();
    
    if(levelTwo.goalReached())
    {
      score += levelTwo.getPoints();
      
      if(levelThree.goalReached())
      {
        score += levelThree.getPoints();
      }
    }
  }
  
  if(isBonus())
    score *= 3;
  
  return score;
}

Part (b) – playManyTimes method

public int playManyTimes(int num)
{
  play();
  int bestScore = getScore();
  
  for(int g = 2; g <= num; g++)
  {
    play();
    int score = getScore();
    if(score > bestScore)
      bestScore = score;
  }
  
  return bestScore;
}

2022 AP CS Exam Free Response Solutions

• Textbook Free Response Solution
• ReviewAnalysis Free Response Solution
• Data Free Response Solution

WordMatch is #1 from the from the 2021 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap21-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – scoreGuess method

public int scoreGuess(String guess)
{
  int count = 0;

  for(int i = 0; i < secret.length(); i++)
  {
    int j = i + guess.length();

    if(j <= secret.length() && secret.substring(i, j).equals(guess))
      count++;
  }

  return count * (guess.length() * guess.length());
}

I would normally have used indexOf for this problem; however, the description mentioned that the occurrences of guess might overlap (and the second example showed such a situation). This approach seemed more reliable to me.

Part (b) – findBetterGuess method

public String findBetterGuess(String guess1, String guess2)
{
  int score1 = scoreGuess(guess1);
  int score2 = scoreGuess(guess2);
  
  if(score1 > score2)
    return guess1;
  else if(score2 > score1)
    return guess2;
  else
  {
    if(guess1.compareTo(guess2) > 0)
      return guess1;
    else
      return guess2;
  }
}

2021 AP CS Exam Free Response Solutions

• CombinedTable Free Response Solution
• ClubMembers Free Response Solution
• ArrayResizer Free Response Solution

CombinedTable is #2 from the from the 2021 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap21-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – CombinedTable class

public class CombinedTable
{
  private SingleTable t1, t2;

  public CombinedTable(SingleTable t1, SingleTable t2)
  {
    this.t1 = t1;
    this.t2 = t2;
  }
	
  public boolean canSeat(int people)
  {
    int seats = t1.getNumSeats() + t2.getNumSeats() - 2;
    return seats >= people;
  }
	
  public double getDesirability()
  {
    double averageView = (t1.getViewQuality() + t2.getViewQuality()) / 2;

    if(t1.getHeight() == t2.getHeight())
       return averageView;
    else
      return averageView - 10;
  }
}

2021 AP CS Exam Free Response Solutions

• WordMatch Free Response Solution
• ClubMembers Free Response Solution
• ArrayResizer Free Response Solution

ClubMembers is #3 from the from the 2021 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap21-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – addMembers method

public void addMembers(String[] names, int gradYear)
{
  for(String name : names)
    memberList.add(new MemberInfo(name, gradYear, true));
}

Part (b) – removeMembers method

public ArrayList<MemberInfo> removeMembers(int year)
{
  ArrayList<MemberInfo> goodStanding = new ArrayList<MemberInfo>();	

  int i = 0;
  while(i < memberList.size())
  {
    if(memberList.get(i).getGradYear() <= year)
    {
      MemberInfo removed = memberList.remove(i);
      if(removed.inGoodStanding())
        goodStanding.add(removed);
    }
    else
      i++;
  }
		
  return goodStanding;
}

2021 AP CS Exam Free Response Solutions

• WordMatch Free Response Solution
• CombinedTable Free Response Solution
• ArrayResizer Free Response Solution

ArrayResizer is #4 from the from the 2021 AP Computer Science A Free Response problems.

https://apcentral.collegeboard.org/pdf/ap21-frq-computer-science-a.pdf?course=ap-computer-science-a

Part (a) – isNonZeroRow method

public static boolean isNonZeroRow(int[][] array2D, int r)
{
  for(int c = 0; c < array2D[0].length; c++)
    if(array2D[r][c] == 0)
      return false;
  
  return true;
}

Part (b) – resize method

public static int[][] resize(int[][] array2D)
{
  int[][] newArray = new int[numNonZeroRows(array2D)][array2D[0].length];

  int newR = 0;
  for(int oldR = 0; oldR < array2D.length; oldR++)
  {
    if(isNonZeroRow(array2D, oldR))
    {
      // could copy elements within row instead
      newArray[newR] = array2D[oldR];
      newR++;
    }
  }		
 
 return newArray;
}

The postcondition mentions that array2D must be unchanged. I didn’t see anything in the description or in the examples that prohibited copying references to the existing rows. Although I could see an argument that the contents of each row should be copied into the new array (to prevent later modifications to the returned array from changing the original array), I would argue that the above should receive full credit.

2021 AP CS Exam Free Response Solutions

• WordMatch Free Response Solution
• CombinedTable Free Response Solution
• ClubMembers Free Response Solution

Review the ZombiePlant solution with AP CS Tutor Brandon Horn.

Note: This is a new practice problem. Please report any issues with a comment or my contact form. Thanks.

public class ZombiePlant
{
  private final int maxPotency;
  private int treatmentsNeeded;

  public ZombiePlant(int max, int needed)
  {
    maxPotency = max;
    treatmentsNeeded = needed;
  }

  public int treatmentsNeeded()
  {
    return treatmentsNeeded;
  }

  public void treat(int potency)
  {
    if(potency > maxPotency)
    {
      treatmentsNeeded++;
    }
    else
    {
      if(treatmentsNeeded > 0)
        treatmentsNeeded--;
    }
  }

  public boolean isDangerous()
  {
    return treatmentsNeeded > 0;
  }
}

Problem description

This question involves the implementation of a zombie plant treatment system that is represented by the ZombiePlant class. A ZombiePlant object is created with parameters that specify the maximum potency for a successful treatment and the initial number of successful treatments required to cure the plant.

The ZombiePlant class provides a constructor and the following methods.

• treatmentsNeeded, which returns the number of successful treatments required to cure the plant
• isDangerous, which returns true if the plant requires treatment, false otherwise
• treat, which administers a treatment with the specified potency

The following table contains a sample code execution sequence and the corresponding results.

Write the complete ZombiePlant class, including the constructor and any required instance variables and methods. Your implementation must meet all specifications and conform to the example.

See the ZombiePlant solution or review it with AP CS Tutor Brandon Horn.