Homework 5

1
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_0
5/homework.html

• CS 5 website

http//www.cs.hmc.edu/courses/2002/fall/cs5/

• Submission problems or other concerns?

email dodds_at_cs.hmc.edu or bthom_at_cs.hmc.edu
2

• 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 ---------------------------------------- Chr
is 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 ---------------------------------------- Gab
riel 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
3

• 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
4
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
5
bloody instructions which return to plague their
inventor
Macbeth, Act I, Scene 7
???
6
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 lt skipping 9 lines gt 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
7
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
8
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 ?
9
advanceChar
Now we need to worry about making this piece
work...
public static char advanceChar(char c, int n)
10
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?
11
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 static char advanceChar(char c, int
n)
12
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 10y x return a
13
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 gt 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
14
What does exp do? What are x and numTerms
referring to?
exp
public static double exp(double x, int numTerms)
15
power
What does power do? What are base and p referring
to?
public static double power(double base, int p)
16
factorial
What does factorial do? What is n referring to?
public static double factorial(int n)
17
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 gt 1) 10 The result
is 12.179115120485767 Would you like to continue
(yes/no)? no
Inside main
18
This is e2.5 computed using 10 terms of the series
x0
x1
x2
x3




0!
1!
2!
3!
4 terms
19
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_0
5/homework.html

• CS 5 website

http//www.cs.hmc.edu/courses/2002/fall/cs5/

• Submission problems or other concerns?

email dodds_at_cs.hmc.edu or bthom_at_cs.hmc.edu
20

• 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 ---------------------------------------- Chr
is 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 ---------------------------------------- Gab
riel 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
21

• 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
22
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
23
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 lt skipping 9 lines gt 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
24
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
25
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 ?
26
advanceChar
Now we need to worry about making this piece
work...
public static char advanceChar(char c, int n)
27
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?
28
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 static char advanceChar(char c, int
n)
29
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 10y x return a
30
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 gt 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
31
What does exp do? What are x and numTerms
referring to?
exp
public static double exp(double x, int numTerms)
32
power
What does power do? What are base and p referring
to?
public static double power(double base, int p)
33
factorial
What does factorial do? What is n referring to?
public static double factorial(int n)