CMU 15-112: Fundamentals of Programming and Computer Science
Extra Practice for Unit 2 (Due never) Code Tracing (CT) and Reasoning Over Code (ROC) Exercises

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These problems will help you prepare for hw2 and quiz2. 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. def ct1(n,m):
       for i in range(n, 7):
           for j in range(m, -2, -1):
               i = abs(i)
               j = abs(j)
               if i % 2 == 0:
                   print("even", i)
               elif i > 0:
                   print("foo", i)
               if j % 2 == 1:
                   print("odd", j)
               if j > 0:
                   print("bar", j)
           print("almost done!")
       print("done!")
   
   ct1(5,-1)

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2. def ct2(m, n):
       total = 0
       for x in range(m, n+1, 3):
           print('x =', x)
           total += x
       for y in range(m, m+2):
           print('y = ', y)
           total += y
       return total
   
   print(ct2(1,9))

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3. def ct3(z):
       total = 0
       for y in range(z,1,-1):
           if (y % 2 == 0):
               print('skip y =', y)
               continue
           total += y
           if (total > 20):
               print('break at y =', y)
               break
       return total
   
   print(ct3(10))

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4. def ct4(n, m):
       for i in range(1, 2*n, n):
           for j in range(-m, -1, m//3):
               if(i % 4 == j):
                   print("mod", i, j)
               if(i == j):
                   print("equal", i, j)
               elif(j > i):
                   print("greater", i, j)
               else:
                   break
   ct4(2, -5)

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5. def ct5(x):
       y = 3
       while True:
           print(y, end=' ')
           for z in range(1, x*y, 2):
               if (z % 3 == 1):
                   print(z, end=' ');
                   continue
               y += x
               if (y % 5 > 0):
                   print(y, end=' ')
                   break
               print(y, end=' ')
           if (y > 10): return x
           y += 1
   print(ct5(7))

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

1. def rc1(n):
       if ((not isinstance(n, int)) or (n > 100)): return False
       total = 0
       while (n > 0):
           total = 10*total + n%10
           n //= 10
       return (total == 42)

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2. def f(n):
       if (n == 0): return 1
       n = abs(n)
       count = 0
       while (n > 0):
           count += 1
           n //= 10
       return count
   
   def rc2(m):
       if (not(isinstance(m, int)) or (m < 0)): return False
       start = 0
       while True:
           count = 0
           for n in range(start, start+3):
               count += f(n)
           if (count > 9): break
           start += 1
       return (m == start)

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3. def rc3(m):
       if ((not isinstance(m, int)) or (m < 0)): return False
       x = 1
       while (x < m//2): x += 10
       return (x + m == 60)

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4. def rc4(n):
       if (n == 0): return False
       count = 0
       for x in range(0, 100, n):
           count += 1
       return ((count == 5) and (x//10 == x%10 + 4))

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