Added another free response question from 2019 - q3

Added another free response question from 2019 - q3

.gitignore

@@ -23,3 +23,4 @@ pavement.py
 sphinx_settings.json
 pavement.py
 sphinx_settings.json
+pavement.py

_sources/Unit7-ArrayList/2019delimitersQ3a.rst

@@ -0,0 +1,210 @@
+.. qnum::
+   :prefix:  8-22-
+   :start: 1
+
+Free Response - Delimiters A
+------------------------------
+
+..	index::
+	  single: delimiters
+    single: free response
+
+The following is a free response question from 2019. It was question 3 part A on the exam. You can see all the free response questions from past exams at https://apstudents.collegeboard.org/courses/ap-computer-science-a/free-response-questions-by-year.
+
+3.   Many encoded strings contain *delimiters*. A delimiter is a non-empty string that acts as a boundary between
+different parts of a larger string. The delimiters involved in this question occur in pairs that must be *balanced*,
+with each pair having an open delimiter and a close delimiter. There will be only one type of delimiter for each
+string. The following are examples of delimiters.
+
+.. figure:: Figures/2019del1.png
+    :align: center
+    :figclass: align-center
+
+In this question, you will write two methods in the following ``Delimiters`` class.
+
+.. figure:: Figures/2019del2.png
+    :align: center
+    :figclass: align-center
+
+
+Part A
+========
+
+(a) A string containing text and possibly delimiters has been split into *tokens* and stored in
+``String[] tokens``. Each token is either an open delimiter, a close delimiter, or a substring that is not a
+delimiter. You will write the method ``getDelimitersList``, which returns an ``ArrayList``
+containing all the open and close delimiters found in ``tokens`` in their original order.
+
+The following examples show the contents of an ``ArrayList`` returned by ``getDelimitersList`` for
+different open and close delimiters and different ``tokens`` arrays.
+
+.. figure:: Figures/2019del3.png
+    :align: center
+    :figclass: align-center
+
+.. figure:: Figures/2019del4.png
+   :align: center
+   :figclass: align-center
+
+
+Check your understanding of the question
+=========================================
+
+.. clickablearea:: delim_find_parts_ca
+    :question: Click on the part of the sentences below with the type of thing passed to the method <code>getDelimitersList</code> and the type it returns.
+    :iscode:
+    :feedback: Variable declarations start with a type and then a name.
+
+    :click-incorrect:A string:endclick::click-incorrect: containing text and possibly delimiters has been split into *tokens* and stored inTest2:endclick:
+    :click-correct:String[] tokens:endclick:. :click-incorrect:Each token is either an open delimiter, a close delimiter, or a substring that is not a
+    delimiter:endclick:. :click-incorrect: You will write the method :endclick::click-incorrect:getDelimitersList:endclick:, :click-incorrect: which returns an:endclick: :click-correct:ArrayList:endclick::click-incorrect:
+    containing all the open and close delimiters found in tokens in their original order.:endclick:
+
+
+.. mchoice:: delim_cu_mc_1
+   :answer_a: array
+   :answer_b: List
+   :answer_c: String
+   :answer_d: ArrayList
+   :correct: a
+   :feedback_a: tokens is an array of Strings
+   :feedback_b: Check again
+   :feedback_c: Check again
+   :feedback_d: Check again
+
+   What type is tokens?
+
+.. mchoice:: delim_cu_mc_2
+   :answer_a: int
+   :answer_b: String
+   :answer_c: List
+   :answer_d: double
+   :correct: b
+   :feedback_a: Check again.
+   :feedback_b: Yes, tokens is an array of strings.
+   :feedback_c: Check again.
+   :feedback_d: Check again.
+
+   What type of thing is in tokens?
+
+.. mchoice:: delim_cu_mc_3
+   :answer_a: int
+   :answer_b: String
+   :answer_c: List
+   :answer_d: double
+   :correct: c
+   :feedback_a: Check again.
+   :feedback_b: Check again.
+   :feedback_c: It returns a list of strings, which is actually an ArrayList.
+   :feedback_d: Check again.
+
+   What type of thing does getDelimitersList return?
+
+
+How to Solve Part A
+=====================
+
+The method ``getDelimtersList`` needs to return an ``ArrayList`` of ``Strings`` containing all the open and close delimiters found in the ``tokens`` array in their original order.
+
+This implies that the code needs to create an empty ``ArrayList`` of type ``String``.  Let's call it ``delList``.  The code will loop through the strings in the array ``tokens`` from the start to the end and if the current string is equal to either the ``openDel`` or ``closeDel`` it adds that string to the end of delList.  Finally it should return delList.
+
+.. mchoice:: delim_solve_mc_1
+   :answer_a: delList = new ArrayList&lt;String&gt;();
+   :answer_b: ArrayList&lt;String&gt; delList = new ArrayList&lt;String&gt;;
+   :answer_c: ArrayList&lt;String&gt; delList = new List&lt;String&gt;();
+   :answer_d: ArrayList&lt;String&gt; delList = new ArrayList&lt;String&gt;();
+   :correct: d
+   :feedback_a: You must declare the type for delList
+   :feedback_b: You must include the () when creating a new object
+   :feedback_c: You must create an ArrayList using a concrete subclass like ArrayList
+   :feedback_d: The declared type must be the same or a parent class of the actual type.
+
+   Which Java expression correctly creates an empty ArrayList of type String called delList?
+
+.. mchoice:: delim_solve_mc_2
+   :answer_a: while
+   :answer_b: for
+   :answer_c: for-each
+   :answer_d: nested for loop
+   :correct: c
+   :feedback_a: You can use a while loop, but it would make your code more error prone than another type of loop
+   :feedback_b: You can use a for loop, but it would make your code more error prone than another type of loop
+   :feedback_c: Since you need to loop through all the strings in the array tokens in order, a for-each loop would be best
+   :feedback_d: There is no need for a nested loop in this situation
+
+   Which loop would be best for this situation?
+
+.. mchoice:: delim_solve_mc_3
+   :answer_a: delList.set(0,item);
+   :answer_b: delList.add(0,item);
+   :answer_c: delList.remove(item);
+   :answer_d: delList.add(item);
+   :correct: d
+   :feedback_a: This would change the value at index 0 to item.
+   :feedback_b: This would add item at index 0 and move right any other items in the list
+   :feedback_c: This would remove item from the list
+   :feedback_d: This adds item to the end of the list
+
+   Which code adds item to the end of the list called delList?
+
+.. mchoice:: delim_solve_mc_4
+   :answer_a: if (token == openDel && token == closeDel)
+   :answer_b: if (token == openDel || token == closeDel)
+   :answer_c: if (token.equals(openDel) && token.equals(closeDel))
+   :answer_d: if (token.equals(openDel) || token.equals(closeDel))
+   :correct: d
+   :feedback_a: You should use .equals with strings and || for or
+   :feedback_b: You should use .equals with strings
+   :feedback_c: You should use || for or not &&
+   :feedback_d: This returns true when openDel or closeDel have the same characters as token
+
+   Which code correct checks if token is equal to (has the same characters as) openDel or closeDel?
+
+
+Write the Code
+==================
+
+Complete the method ``getDelimitersList`` below.  The main method contains code to test your solution.
+
+.. activecode:: frq2019Q3A-delim
+   :language: java
+
+   import java.util.*;
+   public class Delimiters
+   {
+
+       /** The open and close delimiters **/
+       private String openDel;
+       private String closeDel;
+
+       /** Constructs a Delimiters object were open is the open delimiter and close is the
+        *  close delimiter.
+        *  Precondition: open and close are non-empty strings
+        */
+       public Delimiters (String open, String close)
+       {
+           openDel = open;
+           closeDel = close;
+       }
+
+       /** Returns an ArrayList of delimiters from the array tokens, as described in part (a). */
+       public ArrayList<String> getDelimtersList(String[] tokens)
+       {
+           /* to be implemented in part a */
+       }
+
+       public static void main(String[] args)
+       {
+           Delimiters d1 = new Delimiters("(", ")");
+           String[] tokens = {"(", "x + y", ")", " * 5" };
+           ArrayList<String> res1 = d1.getDelimtersList(tokens);
+           System.out.println("It should print [(, )] and it prints" + res1);
+
+           Delimiters d2 = new Delimiters("<q>", "</q>");
+           String[] tokens2 = {"<q>", "yy", "</q>", "zz", "</q>"};
+           ArrayList<String> res2 = d2.getDelimtersList(tokens2);
+           System.out.println("It should print [<q>, </q>, </q>] and it prints" + res2);
+
+
+       }
+   }