CMU 15-112: Fundamentals of Programming and Computer Science
Extra Practice for Unit 5 (Due never) Code Tracing (CT) and Reasoning Over Code (ROC) Exercises

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


1. Trace #1:
   
   def onesDigit(n): return n%10 def ct1(L): for i in range(len(L)): L[i] += sum(L) + max(L) return sorted(L, key=onesDigit) a = [2,1,0] print(ct1(a)) print(a)


2. Trace #2:
   
   def ct2(a, b): a += [3] a = a + [4] for c in a: for i in range(len(b)): if (b[i] not in a): print("A", end="") b[i] += c elif (c % 2 == 1): print("B", end="") b += [c] elif (b[-1] != c): print("C", end="") b = b + [c] return (a,b) a = [4] b = [2,3] print(ct2(a,b)) print(a,b)


3. Trace #3:
   
   def ct3(L): result = [ ] M = [L[i]*10**i for i in range(len(L))] for val in M: result.extend([val, L.pop()]) return result L = [2,5,3] M = ct3(L) print(L, M)


4. Trace #4:
   
   def ct4(L): result = [ ] M = L[:] # same as M = copy.copy(L) if (M == L): result.append(1) if (M is L): result.append(2) if (M[0] == L[0]): result.append(3) if (M[0] is L[0]): result.append(4) return result print(ct4([5,7,6]))


5. Trace #5:
   
   def ct5(L): M = L L += [4] M = M + [5] print(L, M) ct5(list(range(1)))


6. Trace #6:
   
   def ct6(): print([3,2,1] > [3,2]) a = [1] b = a c = copy.copy(a) a += [2] a = a + [3] print(a, b, c) a = [2,3,5,3,2] a.remove(2) v = a.pop(2) print(a, v) L = list(range(1,7,2)) M = [v**2 for v in L] N = [v*10 for v in M if v < 10] print(L, M, N) L = ['A', 'BC', 'D'] print('xy'.join(L)) ct6()


7. Trace #7:
   
   import copy a = [1,2,3,4] (b,c) = (a, copy.copy(a)) print((a == b), (a == c)) print((a is b), (a is c)) print((a[0] is b[0]), (a[0] is c[0])) a = [1,2] (b,c) = (a, copy.copy(a)) b[0] += 10 c[1] += 100 for L in [a,b,c]: print(L) a = [1,2] (b,c) = (a, copy.copy(a)) a[0] += 1 b[0] += 2 c[1] += 3 a[0] = c[0] b[0] = a[1] for L in [a,b,c]: print(L) print() a = list(range(2,10,7)) (b, c) = (a, a[:2]) b[0] += 3 a += [3] a = a + [4] print(c + [b[0]]) print(c.append(b[1])) print(a, b, c)


8. Trace #8:
   
   import copy def f(a, b): a = copy.copy(a) a[0] = b[1] b[0] = a[1] return a + b a1 = a2 = list(range(5,7)) b1 = b2 = list(range(2)) a1 = f(a1, b1) print(a1, a2, b1, b2)


9. Trace #9:
   
   def onesDigit(n): return n%10 def ct(L): for i in range(len(L)): L[i] += sum(L) + max(L) return sorted(L, key=onesDigit) a = [2,1,0] print(ct(a)) print(a)


10. Trace #10:
    
    def ct(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(ct(lst)) print(lst)

---

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


1. RC #1:
   
   def rc1(M): assert(isinstance(M, list) and (len(M) == 5)) for i in range(-1, 3): assert(M[i] == M[i-1] + i) return (sum(M) == 15)


2. RC #2:
   
   def rc2(L): assert((isinstance(L, list)) and (None not in L)) i = 0 while (L[i] != None): j = L[i] L[i] = None i = j a = [None]*2 return (L == a + [-1] + a)


3. RC #3:
   
   def rc1(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])


4. RC #4:
   
   import copy def rc(a): assert(sorted(a) == list(range(5,9))) b = copy.copy(a) for i in range(len(b)): b[len(b)-1-i] *= i return ((b[0] == 18) and (min(a) == b[2]) and (a[1] > a[3]))

---