Spring 2018 Midterm Exam 1 March 1, You may not use any books, notes, or electronic devices during this exam.

Transcription

1 Spring 2018 Midterm Exm 1 Mrch 1, 2018 Nme: Andrew ID: Recittion Section: You my not use ny books, notes, or electronic devices during this exm. You my not sk questions bout the exm except for lnguge clrifictions. Show your work on the exm to receive credit. You my use the bcks of pges s scrtch pper. Nothing written on the bck of ny pges will be grded. You my complete the problems in ny order you d like; you my wish to strt with the lst three problems, which re worth most of the credit. All code smples run without crshing. Assume ny imports re lredy included s required. Do not use these post-midterm 1 topics/constructs: time-bsed nimtion, sets, mps/dictionries, recursion, or clsses/oop. Don t write nything in the tble below. Question Points Score Totl: 99

2 1. Code Trcing Indicte wht ech will print. Plce your nswer (nd nothing else) in the box below ech block of code. () (5 points) CT1 import string def ct1(s): = "" for i in rnge(len(s)): if s[i] in string.scii_lowercse: s = s.upper() j = ord(s[i]) - ord("a") print(s[i:-j]) elif s[i] in string.scii_uppercse: += s[i::2] print() elif s[i] in string.digits: t = chr(int(s[i]) + ord("a")) = t print() ct1("2cc3h5") Pge 1 of 15

3 (b) (5 points) CT2 import copy def ct2(): b = c = copy.copy() d = copy.deepcopy() c[0][0] = "I" b[0][1] = "luv" b[1] = [3, 4] c[1][0] = "dogs" d[1] = d[0] d[1].pop() c[0].insert(2, "112") b.ppend("cts") print(" =", ) print("b =", b) print("c =", c) print("d =", d) z = [ ["yes", "no"], [35, 42] ] ct2(z) print("z =", z) Pge 2 of 15

4 2. Resoning Over Code For ech function, find vlues of the prmeters so tht the function will return True. Plce your nswer (nd nothing else) in the box below ech block of code. () (5 points) ROC1 def roc1(n): j = k = 0 while (n > 0): p = n % 100 ssert(p > k) (j, k, n) = (j + 1, p, n // 100) return ((j == 4) nd (j + k == 100)) (b) (5 points) ROC2 import string def roc2(, b): x = y = 8 for c in [2:-2:2]: if c in "HACK112": x -= 3 for c in b.split(): if len(c) > 3: continue if c[0].lower() == [1]: y -= 4 return x < y nd x * y == 0 Pge 3 of 15

5 3. Short Answer Answer ech of the following very briefly. () (2 points) Give n exmple of 1-2 lines of Python code tht demonstrtes shortcircuit evlution. (b) (3 points) In the piece of code shown below, wht style rule is being violted, nd wht chnge would you mke to improve the code? Answer ech question with only one sentence. # Chnge the mode when the user enters level number def keypressed(event, dt): if event.chr == "1": dt.level = int(event.chr) dt.title = "Level " + event.chr elif event.chr == "2": dt.level = int(event.chr) dt.title = "Level " + event.chr elif event.chr == "3": dt.level = int(event.chr) dt.title = "Level " + event.chr elif event.chr == "4": dt.level = int(event.chr) dt.title = "Level " + event.chr Style Issue: How to Fix: Pge 4 of 15

6 (c) (3 points) Circle ll of the test cses tht will fil on the code shown below. def isprime(n): if (n <= 2): return Flse for fctor in rnge(2, int(mth.sqrt(n))): if (n % fctor == 0): return Flse return True A. ssert(isprime(2) == True) B. ssert(isprime(10) == Flse) C. ssert(isprime(1) == Flse) D. ssert(isprime(11) == True) E. ssert(isprime(9) == Flse) (d) (3 points) List the three prts of the MVC frmework nd give n exmple of function ssocited with ech prt. Pge 5 of 15

7 (e) (3 points) The piece of code shown here is supposed to implement the function grdereport, which tkes list of student-score tuples nd returns the dt combined together into string. 1: def grdereport(lst): 2: s = "" 3: for item in lst: 4: user = item[0] 5: score = item[1] 6: s += user + ": " + score + "\n" 7: return s However, it hs bug. The bug occurs when grdereport is run on the list: [("Nin", 97), ("Wlt", 67), ("Nikol", 83)] The function should return the string: Nin: 97 Wlt: 67 Nikol: 83 Insted, it throws the error shown below. Trcebck (most recent cll lst): File "midterm.py", line 9, in <module> grdereport([("nin", 97), ("Wlt", 67), ("Nikol", 83)]) File "midterm.py", line 6, in grdereport s += user + ": " + score + "\n" TypeError: Cn't convert 'int' object to str implicitly Circle the prt of the code tht is cusing the error nd write single line of code in the box below tht would fix the error. Pge 6 of 15

8 4. (20 points) Free Response: ispirish(n) nd nthpirish(n) A pirish number ( coined term) is number with ll of the following properties: The number is positive integer nd hs t lest three digits. Ech pir of consecutive numbers in n forms fctor of n. The number does not contin ny double 0s. For exmple, 1248 is pirish. It hs four digits, no 0s, nd 12, 24, nd 48 re ll fctors of it is lso pirish, becuse 20, 02, nd 20 re ll fctors. On the other hnd, 2100 is not pirish becuse it hs two consecutive 0s, 1250 is not pirish since one of the pirs (12) does not divide the number evenly, 28 is not pirish becuse it only hs two digits, is not pirish becuse it is not n integer, nd foo is not pirish becuse it s string. Write the function ispirish(n) tht tkes n vlue n (which is not gurnteed to be number) nd returns True if it is pirish number nd Flse otherwise. Then, write nthpirish(n) tht tkes n integer vlue n nd returns the nth pirish number. For exmple, nthpirish(0) returns 110. You my write ny dditionl helper functions you desire, nd you my use ny progrmming constructs we ve lerned so fr in clss. Pge 7 of 15

9 Additionl Spce for Answer to Question 4 Pge 8 of 15

10 5. (20 points) Free Response: Polybius encryption In this problem you will write the function polybiusencrypt(plintext, keyword) tht tkes two string rguments nd returns string. plintext is the text tht will be encrypted. keyword is secret keyword. The function will use the keyword to encode the plintext using Polybius squre, then return the encoded string. A Polybius squre is constructed by putting the keyword into 5x5 mtrix, then filling the rest of the mtrix with the remining letters of the lphbet (except z ). To encode the plintext, replce ech letter in the string with its row nd column number. The number pirs re then seprted by spces, with no triling spce t the end. You my ssume tht both plintext nd tht keyword do not contin z or ny non-lphbetic chrcters, nd keyword hs no repeted letters. For exmple, if the keyword is "wordup", then the Polybius squre will be: [['w','o','r','d','u'], ['p','','b','c','e'], ['f','g','h','i','j'], ['k','l','m','n','q'], ['s','t','v','x','y']] Given the plintext "roxyoursocks", the encrypted vlue would be " ", since r is in row 0 nd column 2, o is in row 0 nd column 1, x is in row 4 nd column 3, etc. Pge 9 of 15

11 Additionl Spce 1 for Answer to Question 5 Pge 10 of 15

12 Additionl Spce 2 for Answer to Question 5 Pge 11 of 15

13 6. (25 points) Free Response: Grid Animtion Assuming the run() function is lredy written for you, write init(dt), keypressed(event, dt), mousepressed(event, dt), nd redrwall(cnvs, dt) so tht when the nimtion is first run: A. A grid composed of blue cells (ech 20 pixels by 20 pixels) is displyed in the window, with no mrgin. You my ssume the window s width nd height re ech multiples of 20. B. The top left cell is highlighted (colored yellow insted of blue). The nimtion proceeds s follows: A. If the user presses the up or right rrow keys, the highlighted cell moves in the pproprite direction (with the previous cell regining its originl color). For exmple, if the user presses right, the highlighted cell should move right one column. If the user s rrow key press would move the highlighted cell outside of the grid, it insted wrps round to the other side. For exmple, pressing Up in the top row moves the highlighted cell to the bottom row. Only one cell my be highlighted t time. B. If the user clicks on cell, red dimond ppers in tht cell with points in the middle of ech of the cell s four edges. The bckground should remin blue/yellow, depending on whether the cell is highlighted or not. Clicking on cell tht lredy hs dimond mkes the dimond dispper. Multiple dimonds my exist t the sme time. 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 12 of 15

14 Additionl Spce 1 for Answer to Question 6 Pge 13 of 15

15 Additionl Spce 2 for Answer to Question 6 Pge 14 of 15

16 Additionl Spce 3 for Answer to Question 6 Pge 15 of 15