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CS101 Five Questions

Topics covered

Arithmetic operators

Printing output

Manipulating string objects

Generating random numbers

Getting user input

QUESTION 1

Write a program which, given a start time and an end time, calculates the elapsed time (in hours, minutes and seconds). The times in this program use a 24 hour clock, e.g., 15:23:15 is 23 minutes and 15 seconds past 3pm. You can assume that the end time is always later than the start time. The first two lines of your program initialise the variables in the following way (you will need to change the values assigned to these two variables when you test your program):

start = "06:55:55"

end = "07:04:57"

The time elapsed should always be a time between 00:00:00 and 23:59:59. The start time, the end time and time elapsed always have the form “hh:mm:ss”, i.e., a single digit hour, minute or second has a “0” in front of it. Below are four example outputs from the completed program (using different variable values).

Your program must give the correct output in the same format as the outputs in the example below:

Start time: 15:26:12 End time: 21:40:36

Total time elapsed: 06:14:24

Include this exercise in a module (file) named ‘YourUPIA1Q1.py’, e.g., afer023A1Q1.py.

QUESTION 2

Write a program which simulates four transactions on a bank account. Initially the bank account has a balance of $11568. Each transaction is either a negative amount (a withdrawal) or a positive amount (a deposit). The amount of each transaction (withdrawal or deposit) is a random integer between 100 and 150 inclusive. Below is the statement which initialises the variable, balance:

balance = 11568

In the output, the amount of each transaction is displayed inside parentheses following the balance (after the transaction has been applied). The final line of output shows the overall sum of the four transactions.

Hint: in order to create a transaction which is either a withdrawal or a deposit you will find it useful to generate a random number which is either -1 or 1. The random transaction amount is then multiplied by this number.

Below are two example outputs using the completed program. Your program must give a correct output in the same format as the outputs in the example below:

Initial balance: $11568

1: $11674 (106)

2: $11816 (142)

3: $11926 (110)

4: $11815 (-111)

==========================

Sum of transactions: $247

==========================

Include this exercise in a module (file), named ‘YourUPIA1Q2.py’, e.g., afer023A1Q2.py

QUESTION 3

Write a program which prints a 5 letter word (I have used names in my examples) in the form of a parallelogram as in the examples below. Nine lines of the output print sections of the word, the first line prints the first letter of the word, the next line prints the next two letters of the word, etc. , the fifth line prints the whole word and the next three lines contract the word until the last line which prints just the last letter of the word. Each of these 9 lines is indented by two spaces and the whole nine lines are enclosed inside four rows of stars.

word = "MARIA"

Below is example outputs using the completed program (using two different 5 letter words). Your program must give the correct output in the same format as the outputs in the two examples below:

*********

*********

M

AR

ARI

ARIA

MARIA

ARIA

RIA

IA

A

*********

*********

Include this exercise in a module (file), named ‘YourUPIA1Q3.py’, e.g., afer023A1Q3.py.

QUESTION 4

Write a program which encrypts (or decrypts) a message. The message is always 25 letters in length. The last two lines of code below ensure that the message is always 25 letters in length.

1 original_message = "Pagg rm rfomieugisanrn t!"

2 # Makes sure the message is 25 letters in length

3 message = original_message * 25

4 message = message[0: 25]

Copy the above statements which initialise the variables into your program. The program uses the following encryption method. First the 25 letter message is broken up into five 5 letter words, i.e., a five by five square of letters. Then the message is recreated by going down the five by five square of letters from left to right. For example, the message “abcdefghijklmnopqrstuvwxy” is reshaped into five rows:

abcde

fghij

klmno

pqrst

uvwxy

and then the message is reconstructed going down each column starting from the first column to the last column: “afkpubglqvchmrwdinsxejoty”

Below is the three example outputs using the completed program (using three different starting messages).

Your program must give the output in the same format as the outputs in the three examples below.

Origial message: E l ntbidjhraaoiinyyslt!

Encrypted message: Enjoy this brilliant day!

Original message: Meet at 11 in the library

Encrypted message: Ma hbetiere n at1 lr 1tiy

Original message: Ma hbetiere n at1 lr 1tiy

Encrypted message: Meet at 11 in the library

Include this exercise in a module (file), named ‘YourUPIA1Q4.py’, e.g., afer023A1Q4.py.

QUESTION 5

Write a program which creates a word chain. The word chain starts with a word (of any length) and allows the player to create a new word by making one change (which affects two consecutive letters) to the current word. In this way the user creates four new words in the chain. The user is first prompted for the position of the first of the two letters they wish to change (the first letter is position 0), then prompted for the replacement two letters, and then the program prints the changed word. This process is repeated four times. Below is the statement which initialises the variable, word:

word = "frank"

Below are two example outputs using the completed program (using two different starting words). Your program must give the output in the same format as the outputs in the two examples below. Note that the string of “=” symbols is the same length as the final combined chain of words.

Starting word: frank

Position: 0

Replacement letters: b1

1 Word is now: blank

Position: 3

Replacement letters: me

2 Word is now: blame

Position: 3

Replacement letters: st

3 Word is now: blast

Position: 2

Replacement letters: un

4 Word is now: blunt

===================================

frank->blank->blame->blast->blunt->

===================================

Include this exercise in a module (file), named ‘YourUPIA1Q5.py’, e.g., afer023A1Q5.py.