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1 UNIVERSITY OF TORONTO MISSISSAUGA DECEMBER 2014 FINAL EXAMINATION CSC108H5F Instructor: Zingaro, Petersen, Tong Duration: 3 hours Examination Aids: None Student Number: Family Name(s): Given Name(s): The University of Toronto Mississauga and you, as a student, share a commitment to academic integrity. You are reminded that you may be charged with an academic offence for possessing any unauthorized aids during the writing of an exam. Clear, sealable, plastic bags have been provided for all electronic devices with storage, including but not limited to: cell phones, tablets, laptops, calculators, and MP3 players. Please turn off all devices, seal them in the bag provided, and place the bag under your desk for the duration of the examination. You will not be able to touch the bag or its contents until the exam is over. If, during an exam, any of these items are found on your person or in the area of your desk other than in the clear, sealable, plastic bag; you may be charged with an academic offence. A typical penalty for an academic offence may cause you to fail the course. Please note, you CANNOT petition to re-write an examination once the exam has begun. Do not turn this page until you have received the signal to start. In the meantime, please read the instructions below carefully. This final examination paper consists of 7 questions on 20 pages (including this one). When you receive the signal to start, please make sure that your copy of the final examination is complete. Comments and docstrings are not required except where indicated, although they may help us mark your answers. They may also get you part marks if you can t figure out how to write the code. You do not need to put import statements in your answers. You may not use break or continue on this exam. If you use any space for rough work, indicate clearly what you want marked. Assume all input is valid unless otherwise indicated; there is no need to error-check. You may tear the API page off the back of this exam. # 1: /23 # 2: /12 # 3: /10 # 4: /12 # 5: / 6 # 6: / 5 # 7: /12 TOTAL: /80 Page 1 of 20 Good Luck! cont d...

2 Question 1. Part (a) [23 marks] If a dependent child is a person under 18 years of age who does not earn $10,000 or more a year, which expression would define a dependent child? a. age < 18 and salary < b. age < 18 or salary < c. age <= 18 and salary <= d. age <= 18 or salary <= Part (b) What are the values of girls, boys, and children after the following code has been executed? girls = 0 boys = 0 children = girls + boys girls = 15 boys = 12 a. 0, 0, 0 b. 0, 0, 27 c. 15, 12, 0 d. 15, 12, 27 Part (c) [3 marks] There are three variables, a, b and c, which have been initialised to integer values. Write code to shift the values in these variables around so that a is given b s original value, b is given c s original value, and c is given a s original value. The following diagram illustrates the direction of the shifts: Page 2 of 20 cont d...

3 Part (d) What will be the value of the variable z after the following code is executed? x = 1 y = 2 z = 3 if x < y: if y > 4: z = 5 else: z = 6 Part (e) Consider the following block of code, where variables a, b, c, and answer each store integer values: if a > b: if b > c: answer = c else: answer = b elif a > c: answer = c else: answer = a Which of the following sets of values for a, b, and c will cause answer to be assigned the value in variable b? a. a = 1, b = 2, c = 3 b. a = 1, b = 3, c = 2 c. a = 2, b = 1, c = 3 d. a = 3, b = 2, c = 1 Part (f) What will be the value of result after the following code is executed? nums1 = [1, -5, 2, 0, 4, 2, -3] nums2 = [1, -5, 2, 4, 4, 2, 7] result = 0 j = 0 while j < len(nums1): if nums1[j]!= nums2[j]: result = result + 1 j = j + 1 Page 3 of 20 Student #: cont d...

4 Part (g) What is the outcome or likely purpose of the following piece of code? result = 0 for j in range(len(number)): if number[j] < 0: result = result + 1 a. to find the smallest number in the list b. to count the negative numbers in the list c. to sum the negative numbers in the list d. to add 1 to each of the negative numbers in the list e. to find the index of the first negative number in the list Part (h) [2 marks] What is the outcome or likely purpose of the following piece of code? Express your answer as a short phrase, like the phrases provided as possible answers in the previous question. result = 0 for count in range(1, num + 1): result = result + count Part (i) [6 marks] We can represent a list of integers as a sequence of elements arranged from left to right, with the first element at the left and the last element at the right. Using this representation, a programmer wishes to move all elements of a list one place to the right, with the rightmost element being wrapped around to the leftmost position, as shown in this diagram. Page 4 of 20 cont d...

5 Here is the code that performs that shift for a list referred to by the name values: length = len(values) old_right = values[length - 1] for j in range(length - 1, 0, -1): values[j] = values[j - 1] values[0] = old_right For example, if values initially contains the integers [1, 2, 3, 4, 5], once the code has executed it would contain [5, 1, 2, 3, 4]. Write code that will undo the effect of the above code. That is, write code that will move all the elements of the list one place to the left, with the leftmost element being wrapped around to the rightmost position. Part (j) [6 marks] Write a function that will be given a list of integers and will use a loop to calculate and return (as a float) the mean (average) of all the integers in the list. Page 5 of 20 Student #: cont d...

6 Question 2. [12 marks] To the right of each segment of code, show the output it generates, or write Error and briefly describe why the code will not run. (Note: Dictionaries don t maintain order, so if a question contains a dictionary, your output may not list keys in the same order as Python generates. That s okay.) L = [1, 2, 3, 4] for index in range(len(l)): L[index] = L[index] ** 2 print(l) L = [1, 2, 3, 4] for index in range(1, len(l), 2): print(index, L[index]) L = [["1", "2"], ["3", "4"]] for innerl in L: for item in innerl: print(item) L = [["1", "2"], ["3", "4"]] for innerl in L: for item in innerl: item = int(item) print(l) def mystery(s): return s + "!" word = "happy holidays" mystery(word) print(word) def subset_sum(l, start, finish): return sum(l[start:finish]) grades = [90, 100, 95, 70, 85] print(subset_sum(grades, 2, 4)) print(grades) Page 6 of 20 cont d...

7 d = {} months = ["Oct", "Nov", "Dec"] days = [31, 30, 31] for m in months: d[m] = days[m] print(d) d = {} months = ["Oct", "Nov", "Dec"] days = [31, 30, 31] for index in range(len(months)): d[months[index]] = days[index] print(d) d = {} L = [1, 3, 1, 1, 2] for index in range(len(l)): d[l[index]] = d.get(l[index], []).append(index) print(d) count = 4 d = { a : (1, 2), b : (3,)} L = [ a, a ] for item in L: d[item] += count count += 1 print(d) The following two questions use a file called ages.csv. Here is the contents of that file: Andrew,5 Margaret,3 Eleanor,1 f = open("ages.csv") ages = {} for line in f: fields = line.strip().split(",") ages[fields[1]] = fields[0] print(list(ages.keys())) f = open("ages.csv") line = f.readline() line = f.readline() while line: print(line.strip()[-1]) line = f.readline() Page 7 of 20 Student #: cont d...

8 Question 3. [10 marks] You will need the following definitions for the functions below: 1. A mention begins and ends with a space or the end of the tweet. 2. A hashtag begins with # and ends with a space or the end of the tweet. Complete each function according to its docstring description. Part (a) [4 marks] def tags_intersect(tweet_list, hashtag1, hashtag2): """ (list of str, str, str) -> bool Return True iff the two hashtags appear in the same tweet for at least one of the tweets in the tweet list. >>> tlist = [ Why so many #list questions on the exam? #smh,... The #108 profs like lists! ] >>> tags_intersect(tlist, #list, #108 ) False >>> tags_intersect(tlist, #smh, #list ) True """ Page 8 of 20 cont d...

9 Part (b) [6 marks] def index_mentions(tweet_list): """ (list of str) -> dict of {str: list of int} Return a dictionary that maps mentions, as keys, to lists of indices as values. The indices are the indices of tweets in the input tweet_list that contain the mention. >>> tlist = make the exam had too much fun writing the exam. ] >>> index_mentions(tlist) : [0, 1, : : [1]} """ Page 9 of 20 Student #: cont d...

10 Question 4. [12 marks] Suppose that we want to test the functions is_valid_tweet and type_token_ratio. For each function, fill in the testcase table below the function description. In each line of the table, describe one test case. Each test case should evaluate a different category of input. Do not write any code. We have given you one test case per function as an example. Part (a) [6 marks] Recall from Assignment 1 that a valid tweet is between 1 and 140 characters. function: Consider the following def is_valid_tweet(tweet): """(str) -> bool The parameter represents a potential tweet. Return True if and only if the potential tweet is no less than 1 and no more than 140 characters long. """ To describe each test case, provide the tweet you would pass to is_valid_tweet, the return value you expect, and the purpose of the test case. Test Case Description tweet Return Value string of 1 character a True Page 10 of 20 cont d...

11 Part (b) [6 marks] def type_token_ratio(text): """(list of str) -> float Precondition: text is non-empty. Each str in text ends with \n and text contains at least one word. Return the Type Token Ratio (TTR) for this text. TTR is the number of different words divided by the total number of words. """ To describe each test case, provide the list of strings you would pass to type_token_ratio, the return value you expect (as an arithmetic expression, if you prefer), and the purpose of the test. While Assignment 2 was highly concerned with clean words (words with no punctuation), do not consider punctuation or tricky white space issues in the tests for this question. Test Case Description text Return Value list with one sentence containing one word [ word\n ] 1 / 1 Page 11 of 20 Student #: cont d...

12 Question 5. Part (a) [2 marks] [6 marks] Consider the following list and sort in progress. L1 = [10, 8, 3, 5, 1] After 1 pass: L1 = [1, 8, 3, 5, 10] After 2 passes: L1 = [1, 3, 8, 5, 10] What type of sort is being demonstrated and what will the list look like after the next (third) pass? a. Bubble sort, L1 = [1, 3, 5, 8, 10] b. Selection sort, L1 = [1, 3, 5, 8, 10] c. Selection sort, L1 = [1, 3, 5, 10, 8] d. Insertion sort, L1 = [1, 3, 5, 8, 10] e. Insertion sort, L1 = [1, 3, 5, 10, 8] How many passes, total, are required to completely sort the list? 1. Three: we re done. 2. Four: one for each item in the list except the last item 3. Five: one for each item in the list 4. Six: one for each item in the list plus a cleanup pass Part (b) Consider the following list and sort in progress. L1 = [9, 16, 1, 8, 5] After 1 pass: L1 = [9, 16, 1, 8, 5] After 2 passes: L1 = [1, 9, 16, 8, 5] What type of sort is being demonstrated and what will the list look like after the next (third) pass? a. Bubble sort, L1 = [1, 8, 9, 16, 5] b. Selection sort, L1 = [1, 8, 9, 16, 5] c. Selection sort, L1 = [1, 5, 9, 16, 8] d. Insertion sort, L1 = [1, 8, 9, 16, 5] e. Insertion sort, L1 = [1, 5, 9, 16, 8] Page 12 of 20 cont d...

13 Part (c) Consider the following list and sort in progress. L1 = [9, 16, 1, 8, 5] After 1 pass: L1 = [9, 16, 1, 5, 8] After 2 passes: L1 = [9, 16, 1, 5, 8] What type of sort is being demonstrated and what will the list look like after the next (third) pass? a. Bubble sort, L1 = [9, 1, 5, 8, 16] b. Selection sort, L1 = [9, 1, 5, 8, 16] c. Selection sort, L1 = [16, 1, 5, 8, 9] d. Insertion sort, L1 = [9, 1, 5, 8, 16] e. Insertion sort, L1 = [16, 1, 5, 8, 9] Part (d) Here is a list and that list after each pass of a sort. Which sort is this? [5, 9, 0, 4, 6, 8, 2] [5, 9, 0, 4, 6, 8, 2] [0, 5, 9, 4, 6, 8, 2] [0, 4, 5, 9, 6, 8, 2] [0, 4, 5, 6, 9, 8, 2] [0, 4, 5, 6, 8, 9, 2] [0, 2, 4, 5, 6, 8, 9] a. Bubble sort b. Selection sort c. Insertion sort d. Merge sort Part (e) Consider the following list. How many swap operations are performed by selection sort, sorting in nondescending order? (If an item is already in the correct position, it is not swapped.) [9, 13, 6, 3, 1] a. 3 b. 4 c. 5 d. 8 e. 9 Page 13 of 20 Student #: cont d...

14 Question 6. [5 marks] What is the time complexity of each of the following pieces of code? Part (a) def mystery(l): index = 0 while 2 ** index < len(l): index += 1 Part (b) def mystery(l): index = 0 while index < len(l): index2 = 0 while index2 < index: index2 += 1 index +=1 Part (c) def mystery(l): index = 0 while index < 1000: index2 = 0 while index2 < len(l): index2 += 1 index +=1 Part (d) def mystery(l): index = 0 while index < 1000: index2 = 0 while index2 < index: index2 += 1 index +=1 Part (e) def mystery(l): index = 0 while index < len(l): index2 = 1 while index2 < len(l): index2 *= 2 index +=1 Page 14 of 20 cont d...

15 Question 7. [12 marks] class Character(object): # same as "class Character:" def init (self, name, game): self.name = name self.game = game def str (self): return "{0} from {1}".format(self.name, self.game) def repr (self): return "Character( {0}, {1} )".format(self.name, self.game) class Enemy(Character): def str (self): return "The Fearsome {0} from {1}".format(self.name, self.game) Part (a) [2 marks] What is displayed when these lines are entered on the console? >>> ch = Character("Link", "Zelda") >>> str(ch) >>> ch >>> ch = Enemy("Goomba", "SMB") >>> str(ch) >>> ch Part (b) [3 marks] Write a new class, Hero, that extends Character. Objects of the class should have an additional attribute, rating, which is set by the constructor. Page 15 of 20 Student #: cont d...

16 Part (c) [7 marks] Write a new class, Characters, that stores Character objects organized by the game they come from. Here is an example that shows what happens when your class is used: >>> chars = Characters() >>> chars.games() [] >>> chars.characters("zelda") [] >>> str(chars) >>> chars.add(character("link", "Zelda")) >>> chars.add(enemy("goomba", "SMB")) >>> chars.add(enemy("koopa", "SMB")) >>> chars.games() # The games may be in the list in any order [ SMB, Zelda ] >>> chars.characters("smb") # The characters may be in the list in any order [ Koopa, Goomba ] >>> str(chars) # The order of games and characters may vary SMB: The Fearsome Koopa from SMB The Fearsome Goomba from SMB Zelda: Link from Zelda Page 16 of 20 cont d...

17 [Space for previous question] Total Marks = 80 Page 17 of 20 Student #: cont d...

18 [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 18 of 20 cont d...

19 Short Python function/method descriptions: builtins : input([prompt]) -> str Read a string from standard input; return that string with no newline. The prompt string, if given, is printed without a trailing newline before reading. len(x) -> int Return the length of the list, tuple, dict, or string x. max(iterable) -> object max(a, b, c,...) -> object With a single iterable argument, return its largest item. With two or more arguments, return the largest argument. min(iterable) -> object min(a, b, c,...) -> object With a single iterable argument, return its smallest item. With two or more arguments, return the smallest argument. print(value,..., sep=, end= \n ) -> NoneType Prints the values. Optional keyword arguments: sep: string inserted between values, default space. end: string appended after the last value, default newline. open(name[, mode]) -> file Open a file. Legal modes are "r" (read), "w" (write), and "a" (append). range([start], stop, [step]) -> list-like-object of int Return the integers starting with start and ending with stop - 1 with step specifying the amount to increment (or decrement). If start is not specified, the list starts at 0. If step is not specified, the values are incremented by 1. dict: D[k] -> object Return the value associated with the key k in D. del D[k] Remove D[k] from D. k in d -> bool Return True if k is a key in D and False otherwise. D.get(k) -> object Return D[k] if k in D, otherwise return None. D.keys() -> list-like-object of object Return the keys of D. D.values() -> list-like-object of object Return the values associated with the keys of D. D.items() -> list-like-object of tuple of (object, object) Return the (key, value) pairs of D, as 2-tuples. file: F.close() -> NoneType Close the file. F.read() -> str Read and return all data until EOF (End Of File) is reached. F.readline() -> str Read and return the next line from the file. Retain newline. Return an empty string at EOF (End Of File). F.readlines() -> list of str Call readline() repeatedly and return a list of the lines so read until EOF (End Of File) is reached. Page 19 of 20 Student #: End of Final Examination

20 list: x in L -> bool Return True if x is in L and False otherwise. L.append(x) -> NoneType Append x to the end of L. L.index(value) -> int Return the lowest index of value in L. L.insert(index, x) -> NoneType Insert x at position index of L. L.pop() -> object Remove and return the last item from L. L.remove(value) -> NoneType Remove the first occurrence of value from L. L.reverse() -> NoneType Reverse L *IN PLACE*. L.sort() -> NoneType Sort L in ascending order *IN PLACE*. str: x in s -> bool Return True if x is in s and False otherwise. str(x) -> str Convert an object into its string representation, if possible. S.count(sub[, start[, end]]) -> int Return the number of non-overlapping occurrences of substring sub in string S[start:end]. Optional arguments start and end are interpreted as in slice notation. S.find(sub[, i]) -> int Return the lowest index in S (starting at S[i], if i is given) where the string sub is found or -1 if sub does not occur in S. S.index(sub) -> int Like find but raises an exception if sub does not occur in S. S.isdigit() -> bool Return True if all characters in S are digits and False otherwise. S.lower() -> str Return a copy of S converted to lowercase. S.lstrip([chars]) -> str Return a copy of S with leading whitespace removed. If chars is given and not None, remove characters in chars from s. S.replace(old, new) -> str Return a copy of S with all occurrences of the string old replaced with the string new. S.rstrip([chars]) -> str Return a copy of S with trailing whitespace removed. If chars is given and not None, remove characters in chars from s. S.split([sep]) -> list of str Return a list of the words in S; use string sep as the separator and any whitespace string if sep is not specified. S.strip() -> str Return a copy of S with leading and trailing whitespace removed. S.upper() -> str Return a copy of S converted to uppercase. Page 20 of 20 End of Final Examination