SeatingChart free response answer 2014

SeatingChart is #3 from the from the 2014 AP Computer Science A Free Response problems.

https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap14_frq_computer_science_a.pdf

Part (a) SeatingChart constructor

public SeatingChart(List<Student> studentList, int rows, int cols)
{
    seats = new Student[rows][cols];

    int sIndex = 0;

    for(int c = 0; c < seats[0].length; c++)
    {
        for(int r = 0; r < seats.length; r++)
        {
            if(sIndex < studentList.size())
            {
                seats[r][c] = studentList.get(sIndex);
                sIndex++;
            }
        }
    }
}

When writing a constructor for a class that stores an array or ArrayList as an instance variable, make sure to actually initialize the variable. It is common for students to omit the first line entirely and incorrectly assume that adding/setting initializes the array/list. As with all constructors, make sure to initialize the instance variable rather than incorrectly declaring a new local variable.

See 2D array exercises for additional traversals and other challenges.

Part (b) removeAbsentStudents method

public int removeAbsentStudents(int allowedAbsences)
{
    int removed = 0;

    for(int r = 0; r < seats.length; r++)
    {
        for(int c = 0; c < seats[0].length; c++)
        {
            if(seats[r][c] != null && seats[r][c].getAbsenceCount() > allowedAbsences)
            {
                seats[r][c] = null;
                removed++;
            }
        }
    }

    return removed;
}

2014 AP CS Exam Free Response Solutions

Additional resources for 2D arrays

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