Fall 2018 Midterm 1 October 11, ˆ You may not ask questions about the exam except for language clarifications.

Transcription

1 Fll 2018 Midterm 1 October 11, 2018 Nme: Andrew ID: Recittion Section: ˆ You my not use ny books, notes, extr pper, or electronic devices during this exm. There should be nothing on your desk or chir side from this exm nd ny writing implements. ˆ You my not sk questions bout the exm except for lnguge clrifictions. ˆ Show your work on the exm to receive credit. ˆ You my use the bcks of pges s scrtch pper. Nothing written on the bck of ny pges will be grded. ˆ You my complete the problems in ny order you d like; you my wish to strt with the free response problems, which re worth most of the credit. ˆ All code smples run without crshing unless we stte otherwise. ˆ You my ssume tht mth, string, tkinter, nd copy re imported; do not import ny other modules. ˆ Do not use these concepts: time-bsed nimtion, dictionries, sets, nd recursion. Don t write nything in the tble below. Question Points Score Totl: 100

2 1. Short Answer Answer ech of the following very briefly. () (3 points) The following function does some mthemticl computtions. The function works fine but hs mny style violtions. List three different style rules from the style guide tht this code violtes, nd clerly indicte where ech is violted in the code. def homeworkproblem3(x, y): if x%y==0: z=x // y if not x%y==0: return Flse else: result=0 while z>0: result=result + z%10 z = z//10 return result==y return Flse (b) (2 points) Sod from the vending mchine costs $1.80. This function should return True if the sum of elements in the list (representing dollr nd coin vlues) is exctly Why might this ssert sttement fil, given the input list? Briefly nd in generl, how might you void this problem when writing code? def exctchnge(coins): dollrs = 0 for i in rnge(len(coins)): dollrs += coins[i] return dollrs == 1.80 ssert(exctchnge([1, 0.25, 0.25, 0.1, 0.1, 0.1])) Pge 1 of 14

3 (c) (3 points) The function findandremove(lst, myitem), which removes ll instnces of myitem from lst, is written three different wys below. Write whether ech implementtion produces syntx, runtime, or logicl error in the box below it, nd briefly explin wht cuses the error. If there is no error, just write no error. def findandremove(lst, myitem): for i in rnge(len(lst)): if lst[i] == myitem: lst.pop(i) lst = ["", 3, "snrf", 3, 42] findandremove(lst, 3) ssert(lst == ["", "snrf", 42]) def findandremove(lst, myitem): for i in rnge(len(lst) - 1, -1, -1): if lst[i] == myitem: lst.pop(i) lst = ["", 3, [3, 4], "snrf", 3, 42] findandremove(lst, "") ssert(lst == [3, [3, 4], "snrf", 3, 42]) def findandremove(lst, myitem): while i < len(lst): if lst[i] == myitem: lst.pop(i) else: i += 1 lst = ["", 3, [3, 4], "snrf", 3, 42] findandremove(lst, "snrf") ssert(lst == ["", 3, [3, 4], 3, 42]) Pge 2 of 14

4 (d) (2 points) For the following components of the word serch nimtion, mrk whether these components should be considered s prt of the Model, View, or Controller. 1. The size of ech cell is stored s n integer Model View Controller 2. Mouse click hndler dds cell to selection Model View Controller 3. Selected cells re drwn in yellow Model View Controller 4. Lines re drwn through found words Model View Controller 5. A 2D list specifies the letters for ech cell Model View Controller 6. Pressing the s key serches for remining words Model View Controller Pge 3 of 14

5 2. Code Trcing Indicte wht ech piece of code will print. Plce your nswer (nd nothing else) in the box below ech piece of code. () (6 points) CT 1 import copy def ct1(): b = copy.copy() c = copy.deepcopy() [1] = "hck" b[0][1] = 20 c[1][0] = 32 c.ppend(b[0].pop(0)).extend([[0]]) print(":", ) print("b:", b) print("c:", c) z = [ [ "ct", 4 ], [ "dog", 12 ] ] ct1(z) print("z:", z) Pge 4 of 14

6 (b) (6 points) CT 2 def (s): print(":", s) s = s[1:-1] b(s) print(s) def b(s): print("b:", s) s = s + s return s def c(s): print("c:", s) t = "" for x in s: if x not in t: t += x return t s = "mr_roboto" print("out:", (c(b(s)))) Pge 5 of 14

7 3. Resoning Over Code For ech function, find prmeter vlues tht will mke the function return True. Plce your nswer (nd nothing else) in the box below ech block of code. () (5 points) ROC 1 def helper(num): for i in rnge(1, num): if num % i == 0: d = num % 5 c = i return (c, d) def roc1(num): ssert(100 < num < 200), b = helper(num) try: if // 10 == 4 nd // b == 0: return Flse except: return True return Flse (b) (5 points) ROC 2 def roc2(s): for i in rnge(1, len(s) - 1, 2): s = s[:i] + chr(ord(s[i]) - 1) + s[i + 1:] ssert("r" not in s) s = s.replce("b", "r") s = s.replce("y", "b") return s == "october" Pge 6 of 14

8 4. (18 points) Free Response: nthcirculrprime Write the function nthcirculrprime tht tkes non-negtive int n nd returns the nth circulr prime, which is prime number tht does not contin ny 0 s nd such tht ll the numbers resulting from rotting its digits re lso prime. One exmple of circulr prime is 197; note tht this number is circulr prime becuse 197 is prime, s is 971 (rotted left), s is 719 (rotted left gin). Note tht you do not need to write isprime(n); ssume it hs lredy been provided. nthcirculrprime(0) is 2, which is followed by 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, 97, 113, 131, Note: you my not use strings t ll in this problem. Hint: consider writing one or more helper functions! Pge 7 of 14

9 Additionl Spce for Answer to Question 4 Pge 8 of 14

10 5. (25 points) Free Response: Regulr polygon nimtion A polygon is regulr if every ngle is equl nd every side length is equl. Assuming the run() function is lredy written for you, write init(d), keypressed(e, d), mousepressed(e, d), nd redrwall(c, d) so tht when the nimtion is first run: 1. A circle with red outline nd no fill is displyed in the center of the window. Its dimeter should be equl to the window s height or width, whichever is smller. 2. An equilterl tringle ( regulr 3-sided polygon) is drwn such tht its three points touch the edge of the circle. The tringle is blue nd filled in. The nimtion proceeds s follows: 1. If the user presses the up rrow key, the number of points of the inner polygon increses by one. Every point of the polygon should still touch the circle, nd the polygon should remin regulr. For exmple, if the up key is pressed once, the tringle becomes squre. For subsequent up key presses, it becomes pentgon (5 sides), hexgon (6 sides), heptgon (7 sides) nd so forth. 2. If the user presses the down rrow key nd the current polygon hs more thn three points, the number of points in the polygon decreses by one. As before, every point of the polygon should still touch the circle, nd the polygon should remin regulr. If the user presses the down rrow key when only three points remin, nothing hppens. 3. If the user clicks the mouse outside of the circle, the number of points in the polygon should reset to 3. Mke resonble ssumptions for nything not specified here. Do not hrdcode vlues for dt.width or dt.height. We recommend tht, to sve time writing, you bbrevite cnvs, event, nd dt: use c, e nd d, respectively. You should lso use short vrible nmes. Pge 9 of 14

11 Additionl Spce for Answer to Question 5 Pge 10 of 14

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13 6. (25 points) Free Response: longestplindrome A plindrome is word tht reds the sme forwrds nd bckwrds. A few exmple plindromes re level, rcecr, nd wow. Write the function longestplindrome(bord) which tkes 2D list of single-chrcter strings s prmeter nd returns the longest plindrome tht cn be found in ny row or column of the bord. For exmple, given the following bord: bord = [ [ "w", "n", "b", "", "", "j", "t", "q" ], [ "o", "r", "", "c", "e", "c", "", "r" ], [ "w", "x", "l", "e", "v", "e", "l", "z" ] ] we cn construct four plindromes: wow in column 0, in row 0, rcecr in row 1, nd level in row 2. (Note tht ll single-letter chrcters re lso plindromes by definition). In this bord, rcecr would be returned s the longest plindrome. You re gurnteed tht the provided vlue will be 2D list contining only one-chrcter strings, nd tht the list will be rectngulr. If there re multiple plindromes with the longest length, you my return ny one of them. If there re no plindromes (i.e., if the bord is empty), you should return n empty string. Note: you should not look for plindromes in digonls; only serch horizontlly nd verticlly. Hint: consider how you might find the longest plindrome in 1D list of letters. A very similr pproch cn be used here... Pge 12 of 14

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