CMU 15-112 Summer 2020: Fundamentals of Programming and Computer Science
Homework 4 (Due Tue 26-May, at 5pm)

• This assignment is SOLO. This means you may not look at other student's code or let other students look at your code for these problems. See the syllabus for details.


• To start:
  1. Create a folder named 'hw4'
  2. Download hw4.py and cs112_m20_day5_linter.py to that folder
  3. Edit hw4.py using VSCode
  4. When you are ready, submit hw4.py to Autolab. For this hw, you may submit up to 10 times (which is fewer than you've had in the past), but only your last submission counts.
• Do not use sets, dictionaries, or recursion in this assignment.
• Do not hardcode the test cases in your solutions.
• NOTE: We are providing you with far fewer test cases this time around. You should be adding multiple test cases to testNondestructiveRotateList and testDestructiveRotateList.
• NOTE: This homework is going to be graded for style. Make sure that you adhere to the style guide when you're working on this HW, and double check your file against the style guide before you submit to Autolab!

1. nondestructiveRotateList(L, n) [10pts - Mild]
   Write the function nondestructiveRotateList(L, n) which takes a list a and an integer n, and nondestructively modifies the list so that each element is shifted to the right by n indices (including wraparound). The function should then return this new list. For example:

       nondestructiveRotateList([1,2,3,4], 1) -> [4,1,2,3]
       nondestructiveRotateList([4,3,2,6,5], 2) -> [6, 5, 4, 3, 2]
       nondestructiveRotateList([1,2,3], 0) -> [1,2,3]
       nondestructiveRotateList([1, 2, 3], -1) -> [2, 3, 1]
   



2. destructiveRotateList(L, n) [10pts - Mild]
   This function works the same as the previous function, only here it is destructive. That is, it directly changes the list a, so after the call, that exact list is rotated n indices to the right with wraparound, and a new list is not created. As usual for destructive functions, this function returns None. Also: you may not call the nondestructive version here, and in fact, you may not even create a new list (or tuple or other similar data structure) that is longer than 10 elements (you must modify the original list in place).


3. bestScrabbleScore(dictionary, letterScores, hand) [40 pts - Medium]
   Background: In a Scrabble-like game, players each have a hand, which is a list of lowercase letters. There is also a dictionary, which is a list of legal words (all in lowercase letters). And there is a list of letterScores, which is length 26, where letterScores[i] contains the point value for the ith character in the alphabet (so letterScores[0] contains the point value for 'a'). Players can use some or all of the tiles in their hand and arrange them in any order to form words. The point value for a word is 0 if it is not in the dictionary, otherwise it is the sum of the point values of each letter in the word, according to the letterScores list (pretty much as it works in actual Scrabble).
   
   In case you are interested, here is a list of the actual letterScores for Scrabble:

      letterScores = [
      #  a, b, c, d, e, f, g, h, i, j, k, l, m
         1, 3, 3, 2, 1, 4, 2, 4, 1, 8, 5, 1, 3,
      #  n, o, p, q, r, s, t, u, v, w, x, y, z
         1, 1, 3,10, 1, 1, 1, 1, 4, 4, 8, 4,10
      ]
   

   Note that your function must work for any list of letterScores as is provided by the caller.
   
   With this in mind, write the function bestScrabbleScore(dictionary, letterScores, hand) that takes 3 lists -- dictionary (a list of lowercase words), letterScores (a list of 26 integers), and hand (a list of lowercase characters) -- and returns a tuple of the highest-scoring word in the dictionary that can be formed by some arrangement of some subset of letters in the hand, followed by its score. In the case of a tie, the first element of the tuple should instead be a list of all such words in the order they appear in the dictionary. If no such words exist, return None.
   
   Note: there is no fixed dictionary here. Each time we call the function, we may provide a different dictionary! It may contain 100 words or perhaps 100,000 words.


4. runSimpleProgram(program, args) [60pts - Spicy]
   First, carefully watch this video that describes this problem.
   Then, write the function runSimpleProgram(program, args) that works as described in the video, taking a legal program (do not worry about syntax or runtime errors, as we will not test for those cases) and runs it with the given args, and returns the result.
   
   Here are the legal expressions in this language:
   
   
   • [Non-negative Integer]
     Any non-negative integer, such as 0 or 123, is a legal expression.
   
   
   • A[N]
     The letter A followed by a non-negative integer, such as A0 or A123, is a legal expression, and refers to the given argument. A0 is the value at index 0 of the supplied args list. It is an error to set arg values, and it is an error to get arg values that are not supplied. And you may ignore these errors, as we will not test for them!
   
   
   • L[N]
     The letter L followed by a non-negative integer, such as L0 or L123, is a legal expression, and refers to the given local variable. It is ok to get an unassigned local variable, in which case its value should be 0.
   
   
   • [operator] [operand1] [operand2]
     This language allows so-called prefix expressions, where the operator precedes the operands. The operator can be either + or -, and the operands must each be one of the legal expression types listed above (non-negative integer, A[N] or L[N]).
   
   And here are the legal statements in this language (noting that statements occur one per line, and leading and trailing whitespace is ignored):
   
   
   • ! comment
     Lines that start with an exclamation (!), after the ignored whitespace, are comments and are ignored.
   
   
   • L[N] [expr]
     Lines that start with L[N] are assignment statements, and are followed by the expression (as described above) to be stored into the given local variable. For example: L5 - L2 42 This line assigns (L2 - 42) into L5.
   
   
   • [label]:
     Lines that contain only a lowercase word followed by a colon are labels, which are ignored except for when they are targets of jump statements.
   
   
   • JMP [label]
     This is a jump statement, and control is transferred to the line number where the given label is located. It is an error for such a label to not exist, and you may ignore that error.
   
   
   • JMP+ [expr] [label]
     This is a conditional jump, and control is transferred to the line number where the given label is located only if the given expression is positive. Otherwise, the statement is ignored.
   
   
   • JMP0 [expr] [label]
     This is another kind of conditional jump, and control is transferred only if the given expression is 0.
   
   
   • RTN [expr]
     This is a return statement, and the given expression is returned.
   
   Hints:
   1. Do not try to translate the program into Python! Even if you could do so, it is not allowed here. Instead, you are going to write a so-called interpreter. Just keep track of the local variables, and move line-by-line through the program, simulating the execution of the line as appropriate.
   2. You will find it useful to keep track of the current line number.
   3. How long do you run the program? Until you hit a RTN statement! You may assume that will always eventually happen.
   4. We used strip, split, and splitlines in our sample solution, though you of course may solve this how you wish.
   
   Finally, here is a sample test function for you. You surely will want to add some addition test cases. In fact, a hint would be to build your function incrementally, starting with the simplest test cases you can think up, which use the fewest expression and statement syntax rules. Then add more test cases as you implement more of the language.
   def testRunSimpleProgram(): print("Testing runSimpleProgram()...", end="") largest = """! largest: Returns max(A0, A1) L0 - A0 A1 JMP+ L0 a0 RTN A1 a0: RTN A0""" assert(runSimpleProgram(largest, [5, 6]) == 6) assert(runSimpleProgram(largest, [6, 5]) == 6) sumToN = """! SumToN: Returns 1 + ... + A0 ! L0 is a counter, L1 is the result L0 0 L1 0 loop: L2 - L0 A0 JMP0 L2 done L0 + L0 1 L1 + L1 L0 JMP loop done: RTN L1""" assert(runSimpleProgram(sumToN, [5]) == 1+2+3+4+5) assert(runSimpleProgram(sumToN, [10]) == 10*11//2) print("Passed!")


5. CT Practice [15pts - Required]
   
   • To Start:
     1. Download day5-ct-runner.py
     2. Log in with the username and password you received from us.
   • For full credit, you must complete a CT problem in under 5 minutes.
   • For every minute it takes you to complete the problem over 5 minutes you will lose 20% of the score for that problem.
   • You have unlimited attempts to complete each type of problem in the time limit and only your best score is counted.
   • Important: To receive any credit, you must quickly upload a picture of your scrap work and your submission confirmation to this form after getting a correct answer.
   • Your picture should show:
     1. Your box and arrow diagram
     2. Your Andrew ID
     3. The results table, including the correct answer, your answer, and the message "You answered correctly."