COMP10001 Foundations of Computing Final Examination, Semester 2, 2019
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Final Examination, Semester 2, 2019
COMP10001 Foundations of Computing
Part 1: Algorithmic Thinking
Question 1
Evaluate the following expressions, and provide the output in each case.
'snout'[2:]
SEMEsTER 2, 2019
[12 marks]
(b) sorted (['fog', 'cog', 'dog']) |
(c) ('now'[- 1] + 'south'[- 1] + 'hurry'[- 1]) |
(d) sorted ({'owls': 'good', 'more owls': 'not so good'} .values())[1] |
(e) 'nic' not in sorted ('cinema') |
(f) [i%2 for i in range (0, 10, 2)] |
Question 2
[12 marks]
Rewrite the following function, replacing the for loop with a while loop, but preserving the re- mainder of the original code structure:
def all_vowels(word):
vowels = 'aeiou'
seen = ''
for c in word:
if c in vowels:
seen += c
return sorted (seen) == list (vowels)
Question 3
[12 marks]
In project 1, you considered preferential voting, in which a valid vote required a voter to list all candidates once in their preferred order.
The following function orderings(candidates) is intended to recursively generate all possible valid votes for a given set of n candidates.
1 def orderings(candidates):
2
3 if not candidates:
4 return [candidates] 5
6 vote == []
7 for i in range (len (candidates)):
8 current = candidates(i)
9 remainining = candidates[i] + candidates[i+1:]
10 for o in orderings(remaining)
11 vote .append([candidates] + o)
12
13 return vote
However, there are several errors in the given function definition. Identify exactly three (3) errors and specify: (a) the line number where the error occurs; (b) the type of error, as syntax, logic or runtime; and (c) how you would fix each error, in the form of corrected code.
Question 4
[12 marks]
To “obfuscate” text means to make it hard to read. Obfuscating text by substituting or modifying certain characters, can make it more difficult for a casual reader to understand, while still leaving it readable by someone familiar with the rules of modification.
The following function is intended to obfuscate a (lowercase) string of text according to the fol- lowing rules:
1. First, all consecutive duplicate letters are replaced with a single letter; for example, ’hello’ becomes ’helo’ and ’mississippi’ becomes ’misisipi’ .
2. Next, some characters are replaced with numbers/symbols, according to the substitution dic- tionary below; e.g., ’a’ becomes ’@’ and ’e’ becomes ’3’ .
3. Finally, given the updated string after applying rules 1 and 2, convert each character at an even- numbered index (i.e., index positions 0, 2, 4, etc) in this string to uppercase; e.g., the string ’doubt’ becomes ’DoUbT’ .
For example:
>>> obfuscate_text( 'keeping secrets is wise ' )
'K3P !Ng $3cR3T$ ! $ W ! $3 '
Assume you are given the dictionary subs as follows:
subs = {
'a ' : '@ ' ,
's ' : ' $ ' ,
'i ' : ' ! ' ,
'e ' : '3 ' ,
'l ' : ' 1 '
}
As presented, the lines of the function are out of order. Put the line numbers in the correct order and introduce appropriate indentation (indent the line numbers using the columns in the answer table provided to show how the corresponding lines would be indented in your code).
1 obs_text = ''
2 i = 0
3 if short_text[i] in subs:
4 while i < len (short_text):
5 else :
6 obs_text += short_text[i]
7 obs_text += short_text[i] .upper()
8 obs_text += subs[short_text[i]]
9 elif i%2 == 0:
10 i += 1
11 return obs_text
12 def obfuscate_text(text):
13 prev_char = ''
14 if c == prev_char:
15 short_text = ''
16 continue
17 short_text += c
18 for c in text:
19 prev_char = c
Part 2: Constructing Programs
Question 5
[10 marks]
The following function is intended to read in a csv file containing a list of different widgets, and the number of units of each that were sold in a given year, and write out a new csv file which adds
an additional column containing the proportion of total sales represented by each widget. Proportions should be displayed as percentages, shown to two decimal places.
For example, if the file data .csv contains the following:
labels,counts
a,4
b,3
c,5
d,1
After running add_proportions( 'data .csv ' , 'new_data .csv ' ), the file new_data .csv will contain:
labels,counts,proportions
a,4,30 .77
b,3,23 . 08
c,5,38 .46
d,1,7 . 69
Provide code to insert into each of the numbered boxes in the code below to complete the function as described. Note that your code will be evaluated at the indentation level indicated for each box.
import 1
def add_proportions(csv_filename, new_filename):
with open (csv_filename) as csv_file:
reader = csv .DictReader(csv_file, skipinitialspace=True)
header = reader .fieldnames
data = list (reader)
count_sum = 0
for row in 2
count_sum += int (row['count'])
for row in data:
prop = int (row['count']) / count_sum * 100
row['proportion'] = round (prop, 2)
new_header = header + 3
with open ( 4 ) as new_file:
writer = csv .DictWriter(new_file, new_header)
writer .writeheader()
for row in 5
writer .writerow(row)
Question 6
[10 marks]
The aim of this question is to write a single Python statement that generates a given error or excep- tion. Write a single Python statement that generates each of the following errors and exceptions, assuming it is executed in isolation of any other code.
(a) IndexError: list index out of range
(b) TypeError: ’tuple’ object does not support item assignment
(c) AttributeError: ’str’ object has no attribute ’len’
(d) KeyError: 0 |
(e) TypeError: unsupported operand type(s) for +: ’int’ and ’str’ |
Question 7
[18 marks]
Write a function alternate(word) that rearranges the characters of the given lowercase alpha- betic string in word such that vowels and consonants appear in alternating positions. The ordering of vowels and consonants should otherwise remain unchanged.
When no alternating ordering is possible (e.g., because there are too many vowels, or too many consonants) your function should return None.
When there are equal numbers of vowels and consonants, the rearranged word should begin with whichever letter comes earlier in the alphabet.
For example:
>>> alternate( 'tools ' )
tolos
>>> alternate( 'ambulance ' )
mabulanec
>>> alternate( 'headache ' )
ehadaceh
>>> alternate( 'football ' )
None
Part 3: Conceptual Questions
Question 8: Algorithmic Problem Solving
(a) In the context of the analysis of algorithms, briefly explain what is meant by an exact algorithmic approach? [6 marks]
(b) Is binary search an example of a “divide-and-conquer” algorithm? Briefly explain why or why not. [6 marks]
Question 9: Applications of Computing
(a) Briefly describe two applications of artificial intelligence.
[12 marks]
[6 marks]
(b) Briefly explain the concept of anomaly detection and how it can be used in network security. [6 marks]
Question 10: HTML and the Internet
Complete this HTML page:
<! 1 html>
<html xmlns="http://www.w3.org/1999/xhtml " <head>
< 2 http-equiv="Content-Type" <title>COMP10001: The Final Exam</title> </head>
<( *\blank[3]@ *)>
<h1></h1> <p>Starring:
[10 marks]
xml:lang="en" lang="en"> content="text/html; charset=UTF- 8">
< 3 >
<li>You!</li>
<li>Chris, Nic, Marion</li>
<li><(a 4 =" . /images/pikachu .gif" alt="Pikachu!"/></li> </ul>
</p>
</body>
</ 5 >
by filling in the numbered blanks based on selecting from among the following candidate strings:
• a
• body
• DOCTYPE
• ul
• html
• img
• meta
• ol
• src
• td
This is blank space for further answers should you need it. Please ensure that you label the an- swers in this area carefully, and that you indicate on the corresponding question page that your answer can be found here.
2022-10-26