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CSC1015F 2018 test3 solutions
Computer science1015 (CSC1015F)
University of Cape Town
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University of Cape Town ~~ Department of Computer Science
Computer Science 1015F ~~ 2018
Class Test 3
** Solutions **
Enter the following details AND shade in the corresponding blocks to the right with your Student Number.
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Marks : 35 Time : 40 minutes Instructions: a) Answer all questions. b) Write your answers in PEN in the spaces provided. c) Show all calculations where applicable.
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Question 1 2 3 4 5 6 7 8 Max 15 10 10 Marks 0!!!!!!!!!!!!!!!! 1!!!!!!!!!!!!!!!! 2!!!!!!!!!!!!!!!! 3!!!!!!!!!!!!!!!! 4!!!!!!!!!!!!!!!! 5!!!!!!!!!!!!!!!! 6!!!!!!!!!!!!!!!! 7!!!!!!!!!!!!!!!! 8!!!!!!!!!!!!!!!! 9!!!!!!!!!!!!!!!! Marker
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Question 1 – Testing and Arrays [15]
Examine the Q1 module listed at the end of the test and answer the following questions.
(i) Does the function call do_a([1,2,3],0) comprise a complete statement coverage test of the do_a function? Explain your answer.[2]
No. #[1 mark] The lines result=True break have not executed. #[1 mark]
(ii) Write down a set of function calls that will comprise a complete, but minimal, path test of the function do_a. [2]
you need three function calls: one with empty list, e. do_a([],0) one with item in list, e. do_a([1,2,3],1) one with item not in list, e. do_a([1,2,3],0) [2 marks if all correct, 1 mark if two correct function calls, otherwise 0]
(iii)Write down the exact output produced when the Q1. module is executed. [5] _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ #each line has to be absolutely correct in order to get a mark for the line – no half marks t #[1 mark – checks understanding of array access] 4 #[1 mark – checks understanding of function] c #[1 mark – checks understanding of character sorting] [1, 3, 4, 15, 30] #[1 mark – checks understanding that arrays passed by reference] [[0, 1, 2], [1, 2, 3], [2, 3, 4]] #1 mark – checks understanding of do_c function gradient fill
(iv)Write Python code for the function do_d(lst1,lst2) in the Q1 module. This function returns a list that is the result of subtracting the elements in lst1 from the corresponding elements in lst2. The lists must be of the same length; if they are not, do_d returns an empty list. For example, in the Python interpreter, do_d would behave as follows.
Question 2 – Recursion [10]
Examine the Q2 module listed at the end of the test and answer the following questions.
(v) The function do_rec1 in the Q2 module function is recursive. What is the recursive base case for this function? [1]
if s=='':return 0 OR “when the string is empty” or equivalent.
(vi) Explain clearly, briefly and in general terms, what the do_rec1 function does. [1] _________________________________________________________________________ _________________________________________________________________________
It counts the number of 'c' characters in the string 's'. (must be in general terms)
(vii) Write down the exact output when the Q2 module is run in the Python interpreter. [4] ________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 4 #[1 mark] 0 #[1 mark]
1 f fl flo4 #[2 marks]
(viii)Now write a recursive function tot(minimum,maximum) that will return the sum of all the numbers from the minimum to the maximum specified (the sum must include the minimum and maximum). For example, in the Python interpreter, tot would behave as follows. >>>tot(2,4) 9 >>>tot(4,4) 4 >>>tot(5,3) 0 Now complete the function below. [4]
def tot(minimum,maximum): """Returns the sum of the numbers from m to n""" _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ def tot(minimum,maximum): """Returns the sum of the numbers from m to n""" if minimum <=maximum: #[1] return minimum+tot(minimum+1,maximum) #[2] return 0 #[1] Note: zero marks if recursive call missing!! Also., function can be written to count down instead of up.
#1 mark for having 3 lines + #2 marks if all correct, 1 mark if only one mistake
(iv)Now write a function create_d(key_lst,val_lst) that returns a dictionary with the specified key_lst elements as the dictionary keys and the values in val_lst as the corresponding values for the keys. For example, in the Python interpreter, this function behave as follows. >>>create_d(['a','b','c'],[4,5,6]) {'a': 4, 'b': 5, 'c': 6} >>>create_d(["ogre","troll","goblin"],[400,50,60]) {'goblin': 60, 'ogre': 400, 'troll': 50} >>>create_d([2,56],["happy",80]) {2: 'happy', 56: 80}
Now complete the function on the following page. [5] def create_d(key_lst,val_lst):
def create_d(key_lst,val_lst):
out={} #[1]
for i in range(len(key_lst)): #[1]
out[key_lst[i]]=val_lst[i] #[2]
return out #[1]
#or alternative correct answer
_________________Question 2 ______________
#Module Q2
def do_rec1(s,c):
if s=='':return 0
if s[0]==c:
return 1 + do_rec1(s[1:],c)
return do_rec1(s[1:],c)
def do_alt_rec2(s):
n=len(s)
if n>0:
do_alt_rec2(s[:-1])
output=s[:-1]+str(n)
print(output)
print(do_rec1("mississippi",'i'))
print(do_rec1("huckleberry",'a'))
print()
do_alt_rec2("flow")
_________________Question 3 ______________
#Module Q3
file1=open("inp",'r')
lines=file1()
file1()
weights={}
for line in lines:
line=line('\n')
words=line()
for word in words:
weight=len(word)
print(word,weight)
if weight not in weights:
weights[weight]=
else:
weights[weight]+=
file2=open("out",'w')
for w in sorted(weights):
print(w,weights[w],file=file2)
file2()
CSC1015F 2018 test3 solutions
Course: Computer science1015 (CSC1015F)
University: University of Cape Town
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