Extra Practice for Week 5 (Due never) Code Tracing (CT) and Reasoning Over Code (ROC) Exercises

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These problems will help you prepare for the upcoming quizzes, midterms, and final exam. They are optional and you are encouraged to collaborate when working on them.

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Code Tracing (CT)
What will each of these print?

1. Trace #1:
   

   import copy
   
   def ct1(L):
       a = L
       b = copy.copy(L)
       c = copy.deepcopy(L)
       b[1][1] = c[0][0]
       c[1].append(b[1][0])
       a[0] = b[1]
       a[0][0] += b.pop()[0]
       return a,b,c
   
   L = [[1],[2,5]] 
   for val in ct1(L):
       print(val)
   print(L)

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2. Trace #2:
   

   def ct2(a):
       a[1] = "foo"
       a[0], a[2] = a[2], a[0]
       print(a)
       b = a
   
       b.extend([42, "wow" ])
       b.pop()
       print(b)
       c = [] + b
   
       c[1:-1] = ["Hello" , "World" ]
       return c
   
   lst = [15, "1" , "twelve" ]
   print(ct2(lst))
   print(lst)

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3. Trace #3:
   

   import copy
   
   def ct3(L):
       a = L
       b = copy.copy(L)
       c = copy.deepcopy(L)
       b[0] = a[1] * a[1][0]
       a[0][0] += a.pop()[0]
       b[1] = c[0]
       return b
   # Be careful to get the brackets and commas right!
   L = [[1],[2],[3]]
   print(ct3(L))
   print(L)

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4. Trace #4:
   

   import copy
   
   def ct4(L):
       a = L
       b = copy.copy(L)
       c = copy.deepcopy(L)
       a[0] = b[1]
       b[1][1] = c[0]
       c[1].append(b[1])
       a[0][0] += (b[1].pop())[0]
       return (a,b,c)
   # Be careful to get the brackets and commas right!
   for val in ct4([[1],[2,5]]):
       print(val) # prints 3 lines

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5. Trace #5:
   

   import copy
   
   def ct5(a):
       b = a
       (a, c, d) = (b + [b[0]], copy.copy(b), copy.deepcopy(b))
       d[1] = b[0]
       c[1] = d[0]
       b = b[0:1] + b[1:]
       b[0] = [3,4]
       a[0] += [5]
       c[1][0] = 1 + b[0][1]
       a[0][0] = 6 + d[1][0]
       for (s,L) in (("a",a), ("b",b), ("c",c), ("d",d)):
           print(s,L)
   
   a = [list(range(2-i)) for i in range(2)]
   print("start:", a)
   ct5(a)
   print("end:", a)

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Reasoning Over Code (ROC)
Find values for the parameters so the functons return True:

1. RC #1 of 4:
   

   def rc1(n):
       assert((isinstance(n, int)) and (100 <= n <= 999))
       (n, r, c) = (n//100, n//10%10, n%10)
       L = [([0] * c) for row in range(r)]
       # note col is the outer loop
       for col in range(c):
           for row in range(r):
               L[row][col] = n
               n += 1
       return ((L[0][2] - L[0][0] == 10) and
               (sum([len(R) for R in L]) == 20) and
               (sum(L[0]) == 42))
   
   print(rc1(42)) # replace 42 with answer

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2. RC #2 of 4:
   

   def rc2(n):
       assert(isinstance(n, int) and (n > 0))
       (d, total) = (0, 0)
       while (total < 100):
           (d, total) = (d+1, 0)
           a = [d] * d
           b = [a] * d # note: bad way to make a 2d list
           for i in range(d):
               for j in range(d):
                   total += b[i][j]
       return (n == d)
   
   print(rc2(42)) # replace 42 with answer

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3. RC #3 of 4:
   

   def rc3(n):
       a = [[(r+c) for c in range(n)] for r in range(n)]
       b = [a[i][i] for i in range(n)]
       return (sum(b) == 20)
   
   print(rc3(42)) # replace 42 with answer

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4. RC #4 of 4:
   

   def rc4(L):
       assert(sorted(L) == sorted(range(len(L))))
       result = []
       for i in range(len(L)):
           m = L[i]
           for j in range(i, len(L)):
               if (L[j] > m):
                   m = L[j]
           result.append(m)
       return (result == [3, 3, 2, 1])
   
   print(rc4(42)) # replace 42 with answer

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