Homework 5

Homework 5 Sun., 10/6 ( MT sections ) • Due at midnight Mon., 10/7 ( WTh sections ) • Problems http://www.cs.hmc.edu/courses/2002/fall/cs5/week_05/homework.html • CS 5 website http://www.cs.hmc.edu/courses/2002/fall/cs5/ • Submission problems or other concerns? email dodds@cs.hmc.edu or bthom@cs.hmc.edu

Tutors available Academic Computing labs (Parsons) Friday Afternoons 1-4 pm ---------------------------------------- Chris Hwang this week (10/4): Parsons Don Lee this week (10/4): Parsons Daniel Chan this week (10/4): LAC Lab Zach Andree this week (10/4): LAC Lab Annie Chang this week (10/4): LAC Lab Saturday Afternoons 1-4pm ---------------------------------------- Chris Weisiger this week (10/5): Parsons Yu-Min Kim this week (10/5): Parsons Elizabeth Lee-Su this week (10/5): LAC Lab Aaron Homer this week (10/5): LAC Lab Sunday Afternoons 1-4pm ---------------------------------------- Gabriel Neer this week (10/6): Parsons Jeff Brenion this week (10/6): LAC Lab Rene Logan this week (10/6): LAC Lab Linde Activities Center lab

Tutors available Sunday evenings 7-12pm ---------------------------------------- Jenny Xu 6-9 this week (10/6): Parsons Eric Flynn 7-10 this week (10/6): Parsons Melissa Federowicz 7-10 this week (10/6): LAC Lab Max Yi 7-10 this week (10/6): LAC Lab Yu-Min Kim 9-12 this week (10/6): Parsons A. Klose 9-12 this week (10/6): Parsons Matt Beaumont-Gay 9-12 this week (10/6): LAC Lab Chris Hwang 9-12 this week (10/6): LAC Lab Monday Evenings 7-12pm ---------------------------------------- Adam Kangas 7-10 this week (10/7): Parsons Ryka Neher 7-10 this week (10/7): Parsons Max Yi 7-10 this week (10/7): LAC Lab Annie Chang 9-12 this week (10/7): Parsons Paul Scott 9-12 this week (10/7): Parsons John McCollough 9-12 this week (10/7): Parsons Alex Pipkin 9-12 this week (10/7): LAC Lab Chris Wottawa 9-12 this week (10/7): LAC Lab Alex Utter 9-12 this week (10/7): LAC Lab

Problem 2 -- Caesar Cipher Encryption strategy Choose an amount to shift your message. Move each letter that amount. message: shift amount: 3 encrypted message: eorrgb lqvwuxfwlrqv zklfk uhwxuq wr sodjxh wkhlu lqyhqwru

bloody instructions which return to plague their inventor Macbeth, Act I, Scene 7 ???

Problem 2 -- Caesar Cipher Decryption strategy Shift the encrypted message by every possible shift amount Pick out the English text... encrypted message: eorrgb lqvwuxfwlrqv zklfk uhwxuq wr sodjxh wkhlu lqyhqwru all possible shifts: eorrgb lqvwuxfwlrqv zklfk uhwxuq wr sodjxh wkhlu lqyhqwru fpsshc mrwxvygxmsrw almgl vixyvr xs tpekyi xlimv mrzirxsv gqttid nsxywzhyntsx bmnhm wjyzws yt uqflzj ymjnw nsajsytw hruuje otyzxaizouty cnoin xkzaxt zu vrgmak znkox otbktzux isvvkf puzaybjapvuz dopjo ylabyu av wshnbl aolpy pucluavy jtwwlg qvabzckbqwva epqkp zmbczv bw xtiocm bpmqz qvdmvbwz kuxxmh rwbcadlcrxwb fqrlq ancdaw cx yujpdn cqnra rwenwcxa lvyyni sxcdbemdsyxc grsmr bodebx dy zvkqeo drosb sxfoxdyb mwzzoj tydecfnetzyd hstns cpefcy ez awlrfp esptc tygpyezc nxaapk uzefdgofuaze ituot dqfgdz fa bxmsgq ftqud uzhqzfad < skipping 9 lines > xhkkzu ejopnqypekjo sdeyd napqnj pk lhwcqa pdaen ejrajpkn yillav fkpqorzqflkp tefze obqrok ql mixdrb qebfo fksbkqlo zjmmbw glqrpsargmlq ufgaf pcrspl rm njyesc rfcgp gltclrmp aknncx hmrsqtbshnmr vghbg qdstqm sn okzftd sgdhq hmudmsnq bloody instructions which return to plague their inventor cmppez jotusvdujpot xijdi sfuvso up qmbhvf uifjs jowfoups dnqqfa kpuvtwevkqpu yjkej tgvwtp vq rnciwg vjgkt kpxgpvqt

Resources Suppose we have a method that shifts a character c by n letters. Assume these work... char advanceChar(char c, int n) advanceChar(‘h’, 4) is advanceChar(‘z’, 2) is String s = “more java”; length() (tells the length of a String) charAt(int n) (returns the nth char of a String) s.length() is s.charAt(2) is s.charAt( ) is ‘v’

High-level plan char advanceChar(char c, int n) length() (tells the length of a String) charAt(int n) (returns the nth char in a String, starting at 0) We have What to do ?

advanceChar Now we need to worry about making this piece work... public static char advanceChar(char c, int n)

Working with chars 99 122 97 98 123 _ ` a b c d e f g h i j k l m n o p q r s t u v w x y z { } ~ char c = ‘y’; c = (char)(c - 2); c += 5; How do we get back?

Style note // Name: advanceChar // Inputs: a char (c) and an int (n) // Output: the char that is n places // to the right of c, where the // alphabet wraps from ‘z’ to ‘a’. // be sure to comment each method you write! public staticchar advanceChar(char c, int n)

A message from our sponsor public static void main(String[] args) { int x = H.in.nextInt(); int y = H.in.nextInt(); int z = confusing(x,y); H.out.println(“z is ” + z); } public static int confusing(int y, int x) { int a = 0; a = 10*y + x; return a; }

Problem 1 -- finding ex Please input a power (a double) and I will raise e to that power: 2.5 Enter the number of terms you'd like to use (an int >= 1): 10 The result is 12.179115120485767 Would you like to continue (yes/no)? no This is e2.5 computed using 10 terms of the series x0 x1 x2 x3 + + + +… Inside main : 0! 1! 2! 3! 4 terms

What does exp do? What are x and numTerms referring to? exp public static double exp(double x, int numTerms)

power What does power do? What are base and p referring to? public static double power(double base, int p)

factorial What does factorial do? What is n referring to? public static double factorial(int n)

Problem 1 -- finding ex Please input a power (a double) and I will raise e to that power: 2.5 Enter the number of terms you'd like to use (an int >= 1): 10 The result is 12.179115120485767 Would you like to continue (yes/no)? no Inside main :

This is e2.5 computed using 10 terms of the series x0 x1 x2 x3 + + + +… 0! 1! 2! 3! 4 terms