ICS Assignment 2 Solution

Please note: For some questions, starting codes are available. Please fill the blanks in starting codes. For questions without starting codes, you can write the solutions in any form you like. Since we use an auto-grader to grade your code, please strictly name the functions and the submitted files as required by the questions. Moreover, when you submit your answers, you should zip the files, not the whole folder of your answers. Lastly, the starting codes may contain some tests for you to check if your code is correct.





1.    Length of the last word

Write a function lenLastWord that one argument which is a string s consisting of letters, empty spaces, and punctuations (the punctuations are !()-[]{}::’”\,<>./?@#$%^&*_~), print the length of the last word in the string. Put your code in Q1_lenLastWord.py.

Examples:

Input
“hello world.”
“Good morning  !”



Output
5
7




Hint:

●    You may import a package named string, and call string.punctuation to get all the punctuation.
●    You may use a string method, named, .replace()




2.    Number of occurrences

Write a function named “fun1” that takes two arguments, a character c and a string s, which returns the number of occurrences of c in s. Put your code in Q2_numOfOccur.py.

Examples:

function call
fun1(‘l’, ‘hello’)
fun1(‘z’, ‘hello’)



return
2
0



    3. Integer to the Roman letter

Write a function named convert_to_Roman_numeral that accepts an integer between 1 and 3999, convert it into a Roman numeral, and return the Roman number. Here is the conversion table:

‘I’
‘V’
‘X’
‘L’
‘C’
‘D’
‘M’







1
5
10
50
100
500
1000








We take 4 as IV, 9 as IX, 40 as XL, 90 as XC, 400 as CD, 900 as CM, and so on.

Specifically, the numbers from 1 to 10 are expressed as Roman numerals as follows:

I, II, III, IV, V, VI, VII, VIII, IX, X.

The system being basically decimal, tens, and hundreds follow the same pattern. Thus 10 to 100 (counting in tens, with X taking the place of I, L taking the place of V and C taking the place of X):

X, XX, XXX, XL, L, LX, LXX, LXXX, XC, C.

Similarly, 100 to 1000 (counting in hundreds):

C, CC, CCC, CD, D, DC, DCC, DCCC, CM, M.

Examples:

input
1776
1949
3999




output
MDCCLXXVI
MCMXLIX
MMMCMXCIX




Put your code in Q3_int2Rome.py.



Hint: What data structure you will use to connect Roman and Arabic, the list or the dict?

Which one can make your code shorter?
    4. Matrix Mirror

Write a function named “fun1”, which takes an NxN square of numbers, i.e., a 2-D list, and flip it horizontally in place. Put your code in Q4_ matrixMirror.py.

Examples:

m is assigned as
[[1, 2],
[[1, 2, 3],
[[1, 2, 3, 4],

[3, 4]]
[4, 5, 6],
[5, 6, 7, 8],


[7, 8, 9]]
[9, 10, 11, 12],



[13, 14, 15, 16]]




After calling func2(m)






m becomes
[[2, 1],
[[3, 2, 1],
[[4, 3, 2, 1],

[4, 3]]
[6, 5, 4],
[8, 7, 6, 5],


[9, 8, 7],]
[12, 11, 10, 9],



[16, 15, 14, 13]]





5.    Encrypting the contents

Julius Caesar protected his confidential information by encrypting it using a cipher. Caesar’s cipher shifts each letter by a number of letters. If the shift takes you past the end of the alphabet list, just rotate back to the front of the list. In the case of a rotation by 3, w, x, y, and z would map to z, a, b, and c.









You need to encrypt and decrypt a message using Caesar’s cipher. But this time, you need to use an alphabet list (i.e., a codebook) which is a mixture of uppercase and lowercase, and the alphabets are shuffled, not in the alphabet order. The following figure shows an example of the codebook, which is a list.








    1) Write a function name caesarEncrypt() which takes three arguments: message, codebook, shift, where message is a string, codebook is a list of alphabets, and shift is a positive integer. The function returns an encrypted message.
    2) Write a function name caesarDecrypt() which takes three arguments: message, codebook, shift. The function returns a decrypted message.


    • The cipher only encrypts letters; symbols remain unchanged.

    • The encode/decode of a character can be done by finding and computing its indices, but also, you may use the Python dictionary to simplify this process.

When you run the tests in the starting code, you will get the following output. (i.e., the message = “Hello Kitty!”, codebook=the codebook given in the starting code, shift=3)