First Name: Last Name: Q1: /10

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1 CSCA48 Winter 2018 Term Test #1 Student Number: Duration: 90 minutes Aids Allowed: none Markus Login: First Name: Last Name: Carefully read and follow all instructions on this page, and fill in all fields. Write all answers neatly in the space provided, or indicate clearly where your question continues. Please place a checkmark beside your tutorial session Tutorial # Date/Time Room TA Name Check Tut 0001 TUESDAY 16:00-17:00 HW214 Mohammad Tut 0003 WEDNESDAY 16:00-17:00 BV264 William Tut 0006 THURSDAY 09:00-10:00 HW215 Kevin Tut 0008 WEDNESDAY 16:00-17:00 IC120 Mohammad Tut 0009 TUESDAY 10:00-11:00 MW110 Aiyaz Tut 0011 THURSDAY 10:00-11:00 IC120 Prantar Tut 0012 THURSDAY 12:00-13:00 AA207 Priscilla Tut 0015 FRIDAY 10:00-11:00 IC320 Maria Tut 0017 FRIDAY 14:00-15:00 BV363 Maria Tut 0018 TUESDAY 11:00-12:00 MW262 Kevin Tut 0020 TUESDAY 18:00-19:00 IC204 Rohini Tut 0021 TUESDAY 12:00-13:00 HW308 Harshil Tut 0022 FRIDAY 11:00-12:00 IC326 Yufei Cui Tut 0023 WEDNESDAY 13:00-14:00 HW308 Ralph Tut 0025 THURSDAY 10:00-11:00 HW215 Jason Tut 0026 THURSDAY 14:00-15:00 AA206 Eric Do not turn this page until you have received the signal to start. This exam consists of 3 questions plus 1 bonus question in 12 pages. When you receive the signal to start, please make sure that your copy is complete. If you use any space for rough work, indicate clearly what you want marked. Please read all questions thoroughly before starting on any work. The University of Toronto's Code of Behaviour on Academic Matters applies to all University of Toronto Scarborough students. The Code prohibits all forms of academic dishonesty including, but not limited to, cheating, plagiarism, and the use of unauthorized aids. Students violating the Code may be subject to penalties up to and including suspension or expulsion from the University. Q1: /10 Q2: /13 Q3: /6 TOTAL: /29 Page 1 of 12

2 Use the space below for rough work. This page will not be marked unless you clearly indicate the part of your work that you want us to mark. Page 2 of 12

3 1. [10 marks total] Nick wrote a Queue class. He heard that the Code Mangler has been lurking around, permuting lines of code and causing mayhem. So he was extra careful to protect his code against such villainy and vandalism. Unfortunately, it was the Code Stealer who struck. Large portions of Nick s Queue class went missing. Here is what remains. class Queue(): # *** representation invariant and code stolen by Code Stealer *** def init (self): (Queue) -> NoneType Create a new empty Queue. # *** only method left intact, not stolen *** def enqueue(self, item): (Queue, object) -> NoneType Insert <item> in <self>. # put item at beginning of _contents self._contents.insert(0, item) # *** docstring, code and internal comment stolen by Code Stealer *** def dequeue(self): # *** code stolen by Code Stealer *** def isempty(self): (Queue) -> bool Return whether <self> is empty. Page 3 of 12

4 Use the space below for rough work. This page will not be marked unless you clearly indicate the part of your work that you want us to mark. Page 4 of 12

5 Nick is so distraught that he cannot think clearly to restore his code. Please help him. (a) [4 marks] Restore the stolen representation invariant and code for the init method. (b) [5 marks] Restore the stolen docstring, code and internal comment for the dequeue method. (c) [1 mark] Restore the stolen code for the isempty method. Page 5 of 12

6 2. [13 marks total] Consider the following LLNode class, which is used for a node in a linked list of objects. class LLNode: A node for a linked list of objects. def init (self, o, next = None): (LLNode, object, LLNode) - > NoneType Create a new LLNode with data <o> and pointer (to next node in list) <next>. self._data = o self._next = next def get_data(self): (LLNode) -> int Return data from <self>. return (self._data) def get_next(self): (LLNode) -> LLNode Return pointer from <self>. return (self._next) def set_next(self, next): (LLNode, LLNode) -> None Set pointer to <next> in <self>. self._next = next Page 6 of 12

7 Use the space below for rough work. This page will not be marked unless you clearly indicate the part of your work that you want us to mark. Page 7 of 12

8 Consider the ll2str function, which takes a linked list of LLNodes and returns a related string. def ll2str(head): (LLNode) -> str s = "" curr = head while curr!= None: s = s + str(curr.get_data()) curr = curr.get_next() return s Consider the shuffle function, which takes a linked list of LLNodes and rearranges the nodes in some mysterious way. def shuffle(head): taila = head headb = taila.get_next() curr = headb.get_next() headb.set_next(none) while curr!= None: taila.set_next(curr) taila = curr curr = curr.get_next().get_next() taila.get_next().set_next(headb) headb = taila.get_next() taila.set_next(headb) Page 8 of 12

9 (a) [6 marks] Give the output of the following program segment. my_list = LLNode("M", LLNode("Y")) print("1:", ll2str(my_list)) # <<< print statement here shuffle(my_list) print("2:", ll2str(my_list)) # <<< print statement here my_list = LLNode("G", LLNode("A", LLNode("R", LLNode("D", LLNode("E", LLNode("N")))))) print("3:", ll2str(my_list)) # <<< print statement here shuffle(my_list) print("4:", ll2str(my_list)) # <<< print statement here (b) [7 marks] Write a docstring for the shuffle function. Page 9 of 12

10 Use the space below for rough work. This page will not be marked unless you clearly indicate the part of your work that you want us to mark. Page 10 of 12

11 3. [6 marks total] (a) [2 marks] Give a reason why we want to make data types as abstract as possible. (b) [4 marks] When software engineers talk of encapsulation in the context of an object, what are they encapsulating? Page 11 of 12

12 4. [Bonus] We want you to predict how well you scored on this test in comparison to your classmates. Suppose we placed all the test marks from those who wrote this test in a list, then sorted the list so that the highest test mark is at the start of the list, and the lowest is at the end. As we scan this list from start to end, where do you think we would first encounter the test mark you got? Please check one box. (a) in the first 20% of the list (among the highest marks). (b) in the second 20% of the list. (c) in the third 20% of the list. (d) in the fourth 20% of the list. (e) in the last 20% of the list (among the lowest marks). Page 12 of 12