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ECS 32B: Winter 2022

Homework Assignment 1 Rubric

1a: for i in range(1,n):

for j in range(1,n+1):

x = 3 * 4

T(n) = 2n(n-1) = 2n2 - 2n 3 points

valid reasoning for T(n) 2 points

O(n) is n2 3 points

valid proof for O(n) 2 points

1b: for i in range(n):

x = 2 * 3 - 1

T(n) = 3n 3 points

valid reasoning for T(n) 2 points

O(n) is n 3 points

valid proof for O(n) 2 points

1c: i = n

while i > 0:

x = 2 * 3 - 1

i = i - 1

T(n) = 5n + 1 3 points

valid reasoning for T(n) 2 points

O(n) is n 3 points

valid proof for O(n) 2 points

1d: for i in range(1,n+1):

for j in range(1,n+1):

for k in range(1,n+1):

x = 4 + 3 // 2 * 5

T(n) = 4n3 3 points

valid reasoning for T(n) 2 points

O(n) is n3 3 points

valid proof for O(n) 2 points

2a: T(n) = 2

O(n) = 1 or k 6 points

valid proof for O(n) 4 points

2b: T(n) = 4n - 3

O(n) = n 6 points

valid proof for O(n) 4 points

2c: T(n) = 5n3 + 5 + 5n2

O(n) = n3 6 points

valid proof for O(n) 4 points

3. Create a Python function called encoder which expects two arguments.  The first argument  is a string representing a message to be translated into a coded message.  The second argument is a list of lists serving as the key to be used to convert the original string to its coded equivalent.     Each two-element list in the key represents a character that might be found in the original             message paired with the character that will be substituted for the original character while              building the coded message.  The function returns a new string created by replacing every            character in the message with its counterpart. Thisfunction does not print anything. Your           function must be able to work with any code key passed as the second argument as long as it has  the same list of lists structure described above.  Use only the list of lists format described above   and as shown in the examples below. Do not convert the second argument to some other data       structure such as a dictionary....

Here's a program that works...

## this function takes a string and a code key (a list of two

## element lists)...it then builds a new string by looking up

## each character from the input string in the code key,

## retrieving the character associated with the character from

## the input string, and then concatenating the retrieved

## character to the end of the string being build. the function

## returns the new string

def encoder(message, key):

codedmessage = ""

for char in message:

codedmessage = codedmessage + findchar(char, key)

return codedmessage

## this function takes a character and a code key (a list of

## two element lists)...it looks up the character in the code

## key, retrieves the character associated with the input

## character, and returns that character

def findchar(target, key):

for pair in key:

if pair[0] == target:

return pair[1]

return("\\")

First, test with some of the data given in the prompt

e.g.

>>> code1 = [['a', 'n'],['b', 'o'],['c', 'p'],['d', 'q'],

['e', 'r'],['f', 's'],['g', 't'],['h', 'u'],

['i', 'v'],['j', 'w'],['k', 'x'],['l', 'y'],

['m', 'z'],['n', 'a'],['o', 'b'],['p', 'c'],

['q', 'd'],['r', 'e'],['s', 'f'],['t', 'g'],

['u', 'h'],['v', 'i'],['w', 'j'],['x', 'k'],

['y', 'l'],['z', 'm'],[' ', ' ']]

>>> test1 = "the quick brown fox jumped over the lazy dog"

>>> test3 = "we can't stop!"

>>> test4 = ""

>>> encoder(test1, code1)

'gur dhvpx oebja sbk whzcrq bire gur ynml qbt'

>>> encoder(test3, code1)

'jr pna\\g fgbc\\'

>>> encoder(test4, code1)

''

Second, test with a code key that is not in the prompt (your choice)

If all the results are correct, then award all 30 points.

If some of the results are incorrect, then award only 15 points.

If none of the results are correct, then award only 0 points.

In either case, there are some possible deductions:

-5 points if the program prints the string instead of returning the string (check the code)

-5 points if the program modifies the code key (list of lists)...for example, if the program converts the original data structure to a dictionary

-5 points if the program uses more than two loops

but don't let the point total go below 0