# CSE 101: Introduction to Computational and Algorithmic Thinking Lab Assignment #3 solution

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## Description

This lab assignment will give you practice with if-statements, lists and relational operators. You will also debug
and fix a buggy function.
Getting Started
Visit Piazza and download the “bare bones” file lab3.py onto your computer. Open lab3.py in PyCharm and
fill in the following information at the top:
1. your first and last name as they appear in Blackboard
2. your Net ID (e.g., jsmith)
3. your Stony Brook ID # (e.g., 111999999)
4. the course number (CSE 101)
5. the assignment name and number (Lab #3)
Do not, under any circumstances, change the names of the functions or their argument lists. The automated
CodeLoad testing system will be looking for exactly those functions provided in lab3.py. You will be able to
Submit your final lab3.py file to Blackboard by the due date and time. Late work will not be graded.
Code that crashes and cannot be graded will earn no credit. It is your responsibility to test your code by running
Part I: String Sanitizer (20 points)
Write a function sanitize() that takes one argument, st, which is a string that is supposed to contain only
uppercase letters, lowercase letters and digits (numbers in the form of a string).
The function should analyze the string, then separate uppercase letters, lowercase letters and digits into three
different result strings. In the end, the function puts these three strings into a single list, and returns the list.
Note: Please make sure the order of the strings in your final list matches this order:
[string of uppercase letters, string of lowercase letters, string of digits]
CSE 101 – Spring 2018 Lab #3 Page 1
You should also make sure that when you construct the result strings, you should read st from left to right. Please
check the examples below for more detail.
If you encounter a character that’s neither an uppercase letter, nor a lowercase letter nor a digit, your function
should simply ignore that character and proceed through the remainder of the string.
Hint: You may find the following methods helpful. Please also consult the lecture slides.
• Python string.isupper() method (https://www.tutorialspoint.com/python/string isupper.htm)
• Python string.islower() method (https://www.tutorialspoint.com/python/string islower.htm)
• Python string.isdigit() method (https://www.tutorialspoint.com/python/string isdigit.htm)
• Python string.isalpha() method (https://www.tutorialspoint.com/python/string isalpha.htm)
Examples:
Function Call Return Value
sanitize(’kBfmR@93&BvS’) [’BRBS’, ’kfmv’, ’93’]
sanitize(’zs4*ia0QFer5’) [’QF’, ’zsiaer’, ’405’]
sanitize(’@YIc!8pY14nM’) [’YIYM’, ’cpn’, ’814’]
sanitize(’4utb8Z’) [’Z’, ’utb’, ’48’]
sanitize(’7P8VC508@e2LTh’) [’PVCLT’, ’eh’, ’785082’]
sanitize(’2YERJ3pKPZ9qU7nxR1’) [’YERJKPZUR’, ’pqnx’, ’23971’]
sanitize(’B4MP22EY4L6’) [’BMPEYL’, ’’, ’42246’]
sanitize(’8umˆ3bv2gtq3U6wW8O9f’) [’UWO’, ’umbvgtqwf’, ’8323689’]
sanitize(’Z9NYRvfHx%S0ˆP’) [’ZNYRHSP’, ’vfx’, ’90’]
sanitize(’IA8mH!R’) [’IAHR’, ’m’, ’8’]
Note: The quotation marks displayed in the example return values are there to emphasize that the return values
are strings. You should not add quotation marks to your return values.
Part II: Party Cost Calculator (20 points)
Write a function party() that takes two arguments, in the following order:
1. prices: A list of integers that serves as a price book. This list always has four positive integers, with each
element representing the price of a particular item, and always in this order:
• The first element of the list (prices[0]) represents the cost of one ’pizza’.
• The second element of the list (prices[1]) represents the cost of one ’cup’.
• The third element of the list (prices[2]) represents the cost of one ’plate’.
• The fourth element of the list (prices[3]) represents the cost of one ’soda’.
2. shopping list: A list of strings that represents a shopping list. Each item is always one of ’pizza’,
’cup’, ’plate’ or ’soda’. When an item appears multiple times, it means that multiple units of the
item are bought. You may assume that the list will not contains any strings other than these four.
CSE 101 – Spring 2018 Lab #3 Page 2
The function calculates and returns the total cost of the shopping list. However, there are a few discounts that
might apply:
1. If five or more sodas are bought, apply an 8% discount to the total cost of all sodas. This discount can be
used in addition to the entire shopping list discount, described next.
2. Only one of the following discounts to the entire cost might apply:
a. If exactly two pizzas are bought, apply a 10% discount to the total cost of the entire shopping list. This
discount applies to the total cost after discount #1 is considered.
b. If three or more pizzas are bought, apply a 20% discount to the total cost of the entire shopping list.
This discount applies to the total cost after discount #1 is considered.
Again, only one of discounts 2(a) or 2(b) can be applied, not both.
An Example in Detail:
Function call: party([15, 1, 3, 2], [’soda’, ’soda’, ’pizza’, ’cup’, ’cup’, ’soda’,
’pizza’, ’plate’, ’soda’, ’soda’, ’soda’])
Sort it out a little bit, we have:
• ’pizza’ × 2, at \$15 each. We have a 10% discount on the entire cost.
• ’cup’ × 2, at \$1 each
• ’plate’ × 1, at \$3 each
• ’soda’ × 6, at \$2 each. We have an 8% discount on the soda.
Calculate the total price before the 10% total discount is applied:
(15 × 2) + (2 × 1) + (1 × 3) + (6 × 2) × 0.92 = 46.04
Now we can apply the 10% total discount, and get our final return result:
46.04 × 0.9 = 41.436
CSE 101 – Spring 2018 Lab #3 Page 3
Examples:
Function Call Return Value
party([[13, 1, 1, 1], [’plate’, ’soda’, ’soda’,
’plate’, ’plate’, ’pizza’]])
18
party([[10, 1, 2, 1], [’soda’, ’pizza’, ’pizza’,
’soda’, ’plate’, ’plate’, ’cup’, ’soda’, ’cup’,
’cup’, ’plate’, ’soda’, ’cup’]])
30.6
party([[20, 2, 2, 3], [’soda’, ’soda’, ’soda’,
’plate’, ’cup’, ’pizza’, ’soda’, ’soda’, ’soda’,
’plate’, ’soda’, ’pizza’, ’plate’]])
60.587999999999994
party([[13, 2, 4, 2], [’cup’, ’plate’, ’plate’,
’soda’, ’cup’, ’soda’, ’plate’, ’soda’, ’plate’,
’soda’, ’plate’, ’cup’, ’pizza’, ’plate’, ’cup’,
’soda’, ’cup’, ’cup’]])
58.2
party([[11, 2, 3, 2], [’plate’, ’plate’, ’plate’,
’cup’, ’soda’, ’pizza’, ’plate’, ’plate’, ’soda’,
’pizza’, ’pizza’]])
43.2
party([[12, 2, 2, 3], [’soda’, ’cup’, ’cup’, ’soda’,
’soda’, ’cup’, ’cup’, ’cup’]])
19
party([[18, 1, 4, 2], [’soda’, ’cup’, ’plate’,
’soda’, ’cup’, ’soda’, ’soda’, ’soda’, ’plate’,
’cup’, ’soda’, ’pizza’, ’plate’, ’cup’, ’soda’,
’soda’, ’cup’, ’plate’, ’soda’, ’pizza’]])
66.20400000000001
party([[16, 2, 4, 1], [’soda’, ’soda’, ’cup’, ’cup’,
’cup’, ’plate’, ’pizza’, ’pizza’, ’plate’, ’pizza’,
’plate’, ’cup’, ’cup’, ’soda’]])
58.400000000000006
party([[19, 1, 1, 1], [’soda’, ’pizza’, ’cup’,
’plate’, ’soda’, ’cup’, ’plate’, ’cup’, ’pizza’,
’soda’, ’soda’, ’soda’, ’pizza’, ’cup’]])
54.08
party([[19, 2, 3, 3], [’soda’, ’plate’, ’cup’, ’cup’,
’soda’, ’cup’, ’plate’, ’soda’, ’soda’, ’soda’,
’soda’, ’pizza’, ’plate’, ’soda’, ’pizza’, ’soda’,
’plate’, ’plate’, ’cup’]])
74.772
Part III: Debug the Code: Which School Will Junior Attend? (20 points)
In this part you are given some broken code to fix. You are free to just re-write the whole function yourself, but it
is a good time to practice using the debugger.
Fix the function school dilemma() that takes a single argument, age, which represents the age of a person.
You may assume that age is a non-negative integer.
The function is supposed to return which school the person is best suited for, depending on their age:
• if age is less than 6, then return ’Too young for school’.
• if age is more than or equal to 6 and less than 11, then return ’Elementary school’.
CSE 101 – Spring 2018 Lab #3 Page 4
• if age is more than or equal to 11 and less than 14, then return ’Middle school’.
• if age is more than or equal to 14 and less than 18, then return ’High school’.
• if age is more than or equal to 18, then return ’College’.
Remember that Python is a case-sensitive language. Lowercase and uppercase letters are not the same symbols!
Examples:
Function Call Return Value
school dilemma(16) ’High school’
school dilemma(3) ’Too young for school’
school dilemma(44) ’College’
school dilemma(7) ’Elementary school’
school dilemma(2) ’Too young for school’
school dilemma(4) ’Too young for school’
school dilemma(24) ’College’
school dilemma(37) ’College’
school dilemma(13) ’Middle school’
school dilemma(32) ’College’
Note: The quotation marks displayed in the example return values are there to emphasize that the return values
are strings. You should not add quotation marks to your return values.