CMU 15-112: Fundamentals of Programming and Computer Science
Quiz2c
Important notes:
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- You will have brief additional time after we stop to scan and submit your solutions.
- Just before the quiz...
- Have a fully-charged smartphone and laptop, and still plug both in if possible
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black if you don't interact with your screen for a while.
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- Your desk
- The paper you are working on
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- Both of your hands
- Your phone
- During the quiz:
- You may not ask questions during the exam.
- If you are unsure how to interpret a problem, take your best guess.
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- This includes muting yourself at any point; the proctors may mute you though.
- All of these must be visible at all times:
- Your desk
- The paper you are working on
- Your writing utensil(s)
- Both of your hands
- Your phone, with the quiz webpage
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- Stop taking the quiz
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- Keep everything in view (as noted above) until the proctor calls "time".
- When instructed, use your phone to scan your quiz and submit the PDF to Gradescope.
- After submitting to Gradescope, hold your phone up to the webcam to show the receipt.
- Even then, remain in quiz mode until the proctor calls "all clear"
More important notes:
- Write your answers by hand with no calculators, no computers.
- No strings, lists, string or list indexing, or recursion.
- You may call almostEqual(x, y) and roundHalfUp(d) without writing them. Write everything else!
1. Free Response [70 points]
We will say that a number is "summish" (a coined term) if it is an integer >= 1000 where each digit (after the first two digits on the left) is the sum of the previous two digits to its left.
For example, 3257 is summish because 7==2+5 and 5==3+2.
Also, 112358 is summish because 8==3+5, 5==2+3, 3==1+2, and 2==1+1.
Here are the first several summish numbers:
1011, 1123, 1235, 1347, 1459, 2022, 2134, 2246,...
With this in mind, write the function nthSummish(n) that takes a non-negative integer n and returns the nth Summish number. Thus, nthSummish(0) returns 1011.
2. Code Tracing [30 points; 15 points each]
What does the following code print?
Be certain to show your work, and also very clearly circle your answer!
CT 1 of 2:
def ct1(x, y): while (x > y): x -= y y -= 1 r = 0 for z in range(y): r += z return 100*x + r print(ct1(14, 7))
CT 2 of 2:
def ct2(a, b, c): r = 0 for x in range(a, b, c): for y in range(x): r = 10*r + y return r print(ct2(4, 7, 2))
3. Bonus Code Tracing [Up to 4 points; 2 points each]
What does the following code print?
Be certain to show your work, and also very clearly circle your answer!
Bonus CT 1 of 2
def bonusCt1(n): def f(n): r,m = 0,n while m>0: r,m = r+m,m-1 return 2*r-n def g(n): return (f(n+1) - f(n-1)) return f(g(n)) print(bonusCt1(20))
Bonus CT 2 of 2
def bonusCt2(n): r = 0 for x in range(2**n): while (x > 0): r += x%2 x //= 2 return r print(bonusCt2(10))