Q4 - Candy Box

Reference: https://apcentral.collegeboard.org/media/pdf/ap23-frq-comp-sci-a.pdf

Topics:

• 2DArrays

  • Traversal/Searching (Nested For Loops)

  • Null values vs. Objects

  • Move/Delete/Return Objects

• Strings

  • Equals/EqualsIgnoreCase

This would be a good problem for 2D Arrays.

public class Candy

{

   /** Returns a String representing the flavor of this piece of candy */

   public String getFlavor()

   {

       return flavor;

   }

   // The following are the "instance variables, constructors, and methods that [were] not shown"

   // Instance Variable(s)

   private String flavor;

   // Constructor(s)

   public Candy(String flavor)

   {

       this.flavor = flavor;

   }

   /**

    * toString - unnecessary in this case, since it does the same thing as

    * getFlavor. Was provided in case any function in BoxOfCandy used the toString

    * method rather than the getFlavor function.

    *

    * @return String representation of the Candy.

    */

   public String toString()

   {

       return getFlavor();

   }

   // Helpers

   /**

    * toStringPadded is a helper function designed to add spaces before & after the

    * flavor name in order to help with table alignment. It's purely helping the

    * printing capabilities of the BoxOfCandy.

    *

    * @param len the length of the expected String

    * @return the name of the flavor with enough spaces around it to equal the

    *         given len

    */

   public String toStringPadded(int len)

   {

       String flav = getFlavor();

       while (flav.length() < len)

       {

           if (flav.length() + 2 <= len)

               flav = " " + flav + " ";

           else

               flav += " ";

       }

       return flav;

   }

}

public class BoxOfCandy

{

   /** box contains at least one row and is initialized in the constructor */

   private Candy[][] box;

   /**

    * Moves one piece of candy in col, if necessary and possible, so that the box

    * element in row 0 of column col contains a piece of candy, as described in

    * part (a).

    * Return false if there is no piece of candy in column col and true otherwise.

    * Precondition: col is a valid column index in box.

    */

   public boolean moveCandyToFirstRow(int col)

   {

       //to be implemented in part (a)

   }

   /**

    * Removes from box and returns a piece of candy with flavor specified by the

    * parameter, or returns null if no such piece is found, as described in part

    * (b).

    */

   public Candy removeNextByFlavor(String flavor)

   {

       //to be implemented in part (b)

   }

   // The "instance variables, constructors, and methods that [were] not shown"

   // Constructor

   public BoxOfCandy(int numRows, int numCols)

   {

       box = new Candy[numRows][numCols];

   }

   // toString - Prints the entire box of candy.

   public String toString()

   {

       String msg = "";

       int len = calcLongestLength();

       String empty = "";

       String line = "";

       String lineChunk = "";

       for (int i = 0; i < len; i++)

       {

           empty += " ";

           lineChunk += "-";

       }

       for (int i = 0; i < box[0].length; i++)

       {

           line += "-" + lineChunk;

       }

       line += "-\n";

       for (int row = 0; row < box.length; row++)

       {

           msg += line;

           msg += "|";

           for (int col = 0; col < box[row].length; col++)

           {

               Candy cur = box[row][col];

               if (cur != null)

                   msg += cur.toStringPadded(len);

               else

                   msg += empty;

               msg += "|";

           }

           msg += "\n";

       }

       msg += line;

       return msg;

   }

   // Helper Functions

   /**

    * Adds a candy (yumYum) at a given location (row, col) within the box (if it

    * can). - returns true if it was added. - returns false if there was already a

    * candy there.

    *

    * @param yumYum the candy to be added to the box.

    * @param row    the row # (from the top) to begin counting

    * @param col    the col # (from the left) to begin counting

    * @return whether a candy was successfully added.

    */

   public boolean addCandy(Candy yumYum, int row, int col)

   {

       if (box[row][col] == null)

       {

           box[row][col] = yumYum;

           return true;

       }

       return false;

   }

   /**

    * calcLongestLength finds the longest named candy - used to help with box alignment.

    * @return the # of characters in the longest named candy.

    */

   public int calcLongestLength()

   {

       int longest = 0;

       for (int row = 0; row < box.length; row++)

       {

           for (int col = 0; col < box[row].length; col++)

           {

               Candy cur = box[row][col];

               if (cur != null)

               {

                   int len = cur.getFlavor().length();

                   if (len > longest)

                       longest = len;

               }

           }

       }

       return longest;

   }

}